以下，參閱附圖對用於實施本發明之形態進行詳細說明。說明及附圖中對相同或等同的構成要素、構件、處理標註相同符號，並適當省略重複說明。所描繪之各部的比例尺和形狀為便於說明而簡易設定，除非特別指明，則為非限制性解釋。實施形態為示例，對本發明的範圍不做任何限定。實施形態中所描述之所有特徵及其組合，未必為發明的本質。
圖1係概略地表示實施形態之低溫泵10之側剖面圖。圖2係概略地表示圖1所示之低溫泵10之A-A線剖面圖。圖1表示包括用一點鏈線表示之低溫泵中心軸C之剖面。但是，為了便於理解，圖1中示出低溫泵10的低溫低溫板部以及冷凍機的側面而非剖面。
如後述，低溫泵10具有結露抑制結構。
低溫泵10為了提高例如安裝於離子植入裝置、濺射裝置、蒸鍍裝置或其他真空處理裝置的真空腔室且將真空腔室內部的真空度提高至所希望的真空處理所要求之級別而使用。低溫泵10具有用於從真空腔室接收應排出之進氣口12。氣體通過進氣口12而進入到低溫泵10的內部空間14。
低溫泵10可以在將圖式的朝向亦即進氣口12朝向上方之姿勢下設置於真空腔室而使用。但是，低溫泵10的姿勢並不限定於此，低溫泵10可以以其他朝向設置於真空腔室。
另外，以下為了清晰易懂地表示低溫泵10的構成要素的位置關係，有時使用“軸向”、“徑向”這樣的用語。軸向表示通過進氣口12之方向(圖1中，沿通過進氣口12的中心之低溫泵中心軸C之方向)，徑向表示沿進氣口12之方向(與中心軸C垂直的方向)。為方便起見，有時關於軸向，相對靠近進氣口12則稱為“上”，相對較遠則稱為“下”。亦即，有時相對遠離低溫泵10的底部則稱為“上”，相對靠近則稱為“下”。關於徑向，靠近進氣口12的中心(圖1中為中心軸C)則稱為“內”，靠近進氣口12的周緣則稱為“外”。另外，這種表現形式無關於低溫泵10安裝於真空腔室時的配置。例如，低溫泵10可以以使進氣口12沿垂直方向朝下之方式安裝於真空腔室。
又，有時將圍繞軸向之方向稱為“周向”。周向為沿進氣口12之第2方向，且為與徑向正交之切線方向。
低溫泵10具備冷凍機16、第1段低溫板18、第2段低溫板組件20及低溫泵殼體70。第1段低溫板18亦可稱為高溫低溫板部或100K部。第2段低溫板組件20亦可稱為低溫低溫板部或10K部。
冷凍機16例如為吉福德-麥克馬洪式冷凍機(所謂GM冷凍機)等極低溫冷凍機。冷凍機16為二段式冷凍機。因此，冷凍機16具備第1冷卻台22及第2冷卻台24。冷凍機16構成為將第1冷卻台22冷卻至第1冷卻溫度，並將第2冷卻台24冷卻至第2冷卻溫度。第2冷卻溫度為比第1冷卻溫度低的溫度。例如第1冷卻台22被冷卻至65K~120K左右，80K~100K為較佳，第2冷卻台24被冷卻至10K~20K左右。
又，冷凍機16具備結構上由第1冷卻台22支撐第2冷卻台24，同時結構上由冷凍機16的室溫部26支撐第1冷卻台22之冷凍機結構部21。因此，冷凍機結構部21具備沿徑向同軸延伸之第1缸體23及第2缸體25。第1缸體23將冷凍機16的室溫部26連接於第1冷卻台22。第2缸體25將第1冷卻台22連接於第2冷卻台24。室溫部26、第1缸體23、第1冷卻台22、第2缸體25及第2冷卻台24依序排成一條直線。
第1缸體23及第2缸體25各自的內部配設有能夠往復移動的第1置換器及第2置換器(未圖示)。在第1置換器及第2置換器中分別組裝有第1蓄冷器及第2蓄冷器(未圖示)。又，室溫部26具有用於使第1置換器及第2置換器往復移動的驅動機構(未圖示)。驅動機構包括以週期性地反覆向冷凍機16的內部供給與排出工作氣體(例如氦氣)之方式切換工作氣體的流路之流路切換機構。
第1冷卻台22設置於冷凍機16的第1段低溫端。第1冷卻台22為在與室溫部26相反的一側從外側包圍第1缸體23的端部，且圍繞工作氣體的第1膨脹空間之構件。第1膨脹空間為在第1缸體23的內部形成於第1缸體23與第1置換器之間，且容積隨著第1置換器的往復移動而變化之可變容積。第1冷卻台22由比第1缸體23具有高導熱率之金屬材料形成。例如，第1冷卻台22由銅形成，第1缸體23由不鏽鋼形成。
第2冷卻台24設置於冷凍機16的第2段低溫端。第2冷卻台24為在與室溫部26相反的一側從外側包圍第2缸體25的端部，且圍繞工作氣體的第2膨脹空間之構件。第2膨脹空間為在第2缸體25的內部形成於第2缸體25與第2置換器之間，且容積隨著第2置換器的往復移動而變化之可變容積。第2冷卻台24由比第2缸體25具有高導熱率之金屬材料形成。第2冷卻台24由銅形成，第2缸體25由不鏽鋼形成。圖1中示出第2冷卻台24與第2缸體25的界限24b。
冷凍機16與工作氣體的壓縮機(未圖示)連接。冷凍機16使藉由壓縮機加壓之工作氣體在內部膨脹以冷卻第1冷卻台22及第2冷卻台24。膨脹之工作氣體回收至壓縮機而被再次加壓。冷凍機16藉由包括工作氣體的供排及與其同步之第1置換器及第2置換器的往復移動之熱循環的反覆而產生寒冷。
圖示之低溫泵10為所謂的臥式低溫泵。臥式低溫泵通常指冷凍機16以與低溫泵10的中心軸C交叉的(通常為正交)方式配設之低溫泵。冷凍機16的第1冷卻台22及第2冷卻台24沿與低溫泵中心軸C垂直的方向(圖1中為水平方向，冷凍機16的中心軸D的方向)排列。
第1段低溫板18具備放射屏蔽件30和入口低溫板32，並包圍第2段低溫板組件20。第1段低溫板18是為了保護第2段低溫板組件20免受來自低溫泵10的外部或低溫泵殼體70的輻射熱的低溫板。第1段低溫板18熱耦合於第1冷卻台22。藉此，第1段低溫板18被冷卻為第1冷卻溫度。第1段低溫板18在與第2段低溫板組件20之間具有間隙，第1段低溫板18不與第2段低溫板組件20接觸。
放射屏蔽件30為了保護第2段低溫板組件20免受來自低溫泵殼體70的輻射熱而設置。放射屏蔽件30位於低溫泵殼體70與第2段低溫板組件20之間，且包圍第2段低溫板組件20。放射屏蔽件30具有用於從低溫泵10的外部向內部空間14接收氣體的屏蔽件主開口34。屏蔽件主開口34位於進氣口12。
放射屏蔽件30具備：屏蔽件前端36，確定屏蔽件主開口34；屏蔽件底部38，位於與屏蔽件主開口34相反的一側；及屏蔽件側部40，將屏蔽件前端36連接於屏蔽件底部38。屏蔽件前端36構成屏蔽件側部40的一部分。屏蔽件側部40沿軸向從屏蔽件前端36向與屏蔽件主開口34相反的一側延伸，且以沿周向包圍第2冷卻台24之方式延伸。放射屏蔽件30具有屏蔽件底部38封閉之筒形(例如圓筒)的形狀，形成為杯狀。屏蔽件側部40與第2段低溫板組件20之間形成有環狀間隙42。
另外，屏蔽件底部38可以是與屏蔽件側部40獨立的構件。例如，屏蔽件底部38可以是與屏蔽件側部40具有大致相同的直徑之平坦的圓盤，亦可以是在與屏蔽件主開口34相反的一側安裝於屏蔽件側部40。又，屏蔽件底部38可以是其至少一部分被開放。例如放射屏蔽件30可以不藉由屏蔽件底部38而封閉。亦即，屏蔽件側部40可以是兩端被開放。
屏蔽件側部40具有供冷凍機結構部21插入之屏蔽件側部開口44。第2冷卻台24及第2缸體25通過屏蔽件側部開口44而從放射屏蔽件30的外部插入到放射屏蔽件30中。屏蔽件側部開口44為形成於屏蔽件側部40之安裝孔，例如為圓形。第1冷卻台22配置於放射屏蔽件30的外部。
屏蔽件側部40具備冷凍機16的安裝座46。安裝座46為用於將第1冷卻台22安裝於放射屏蔽件30的平坦部分，從放射屏蔽件30的外部觀察時稍微凹陷。安裝座46形成屏蔽件側部開口44的外周。安裝座46在軸向上比屏蔽件前端36更靠近屏蔽件底部38。第1冷卻台22安裝於安裝座46，藉此放射屏蔽件30熱耦合於第1冷卻台22。
入口低溫板32為了保護第2段低溫板組件20免受來自低溫泵10的外部的熱源的輻射熱而設置於屏蔽件主開口34。低溫泵10的外部的熱源例如為安裝有低溫泵10之真空腔室內的熱源。入口低溫板32除了輻射熱之外還能夠限制氣體分子進入。入口低溫板32佔據屏蔽件主開口34的開口面積的一部分以將通過屏蔽件主開口34而流入內部空間14之氣體限制在所希望的量上。入口低溫板32與屏蔽件前端36之間形成有環狀的開放區域48。
入口低溫板32藉由適當的安裝構件而安裝於屏蔽件前端36，且熱耦合於放射屏蔽件30。入口低溫板32經由放射屏蔽件30熱耦合於第1冷卻台22。入口低溫板32例如具有複數個環狀或直線狀的百葉板。或者，入口低溫板32可以是一片板狀構件。
第2段低溫板組件20以包圍第2冷卻台24之方式安裝於第2冷卻台24。藉此，第2段低溫板組件20熱耦合於第2冷卻台24，第2段低溫板組件20被冷卻為第2冷卻溫度。第2段低溫板組件20與第2冷卻台24一起被屏蔽件側部40包圍。
第2段低溫板組件20具備與屏蔽件主開口34相對之頂部低溫板60、複數個(本例中為2個)低溫板構件62及低溫板安裝構件64。
又，如圖1所示，低溫泵10具備低溫板定位構件67。使第2段低溫板組件20熱耦合於第2冷卻台24之導熱部包括低溫板安裝構件64及低溫板定位構件67。頂部低溫板60及低溫板構件62經由低溫板安裝構件64和低溫板定位構件67安裝於第2冷卻台24。
頂部低溫板60及低溫板構件62與屏蔽件側部40之間形成有環狀間隙42，因此頂部低溫板60及低溫板構件62均不與放射屏蔽件30接觸。低溫板構件62被頂部低溫板60所覆蓋。
頂部低溫板60為第2段低溫板組件20中最靠近入口低溫板32之部分。頂部低溫板60在軸向上配置於屏蔽件主開口34或入口低溫板32與冷凍機16之間。頂部低溫板60軸向上位於低溫泵10的內部空間14的中心部。因此，頂部低溫板60的前表面與入口低溫板32之間較寬地形成凝結層的主收容空間65。凝結層的主收容空間65佔內部空間14的上半部分。
頂部低溫板60為軸向上垂直配置之大致平板的低溫板。亦即，頂部低溫板60沿徑向及周向延伸。如圖2所示，頂部低溫板60為比入口低溫板32具有更大尺寸(例如投影面積)之圓板狀面板。但是，頂部低溫板60與入口低溫板32的尺寸關係並不限定於此，可以是頂部低溫板60更小，亦可以是兩者具有大致相同的尺寸。
頂部低溫板60配置成在與冷凍機結構部21之間形成間隙區域66。間隙區域66為在頂部低溫板60的背面與第2缸體25之間沿軸向形成之空白部分。
在低溫板構件62設置有活性碳等吸附材74。吸附材74例如黏著於低溫板構件62的背面。低溫板構件62的前表面發揮凝結面的功能，背面發揮吸附面的功能。可以在低溫板構件62的前表面設置吸附材74。同樣地，頂部低溫板60可以在其前表面及/或背面具有吸附材74。或者，頂部低溫板60可以不具備吸附材74。
2個低溫板構件62夾著低溫泵中心軸C而配置於第2冷卻台24的兩側。低溫板構件62沿與低溫泵中心軸C垂直的平面配置。為了便於理解，圖2中用虛線表示低溫板構件62及低溫板安裝構件64。
2個低溫板構件62配置於低溫泵中心軸C的方向上之第2冷卻台24的上端與下端之間的高度位置。2個低溫板構件62配置於相同的高度。第2冷卻台24在與低溫泵中心軸C垂直的方向(冷凍機16的中心軸D的方向)上之末端具備凸緣部24a。低溫泵中心軸C的方向上之第2冷卻台24的上端及下端依據凸緣部24a而定。亦即，2個低溫板構件62配置於低溫泵中心軸C的方向上之第2冷卻台24的凸緣部24a的上端與下端之間的高度位置。
2個低溫板構件62被設置成相同的部件。2個低溫板構件62具有相同的形狀，且由相同的材料形成。低溫板構件62具有弓形狀、半月狀或半圓狀的形狀。低溫板構件62例如由銅等高導熱率的金屬材料形成，亦可以由例如鎳等鍍層被覆。
如圖2所示，低溫板構件62具有圓弧部78及弦79。向低溫泵中心軸C的方向觀察時，2個低溫板構件62配置成以兩者的中線(冷凍機16的中心軸D)作為對稱軸而相互對稱。2個低溫板構件62的圓弧部78位於以低溫泵中心軸C為中心之相同的圓周上。又，各低溫板構件62具有通過弦79的中點(或低溫泵中心軸C)且以與弦79垂直的線E為對稱軸而線對稱的形狀。
如圖1所示，低溫板定位構件67固定於第2冷卻台24的凸緣部24a，且被第2冷卻台24支撐。低溫板定位構件67形成為上下顛倒之倒L字形。藉由使用低溫板定位構件67，對中心軸D的方向上之冷凍機16的長度的制約得到緩和。即使第2冷卻台24的凸緣部24a位於從低溫泵中心軸C向冷凍機16的中心軸D的方向偏離之位置，亦能夠藉由調整低溫板定位構件67的上邊部67a的長度來將第2段低溫板組件20定位在低溫泵中心軸C上。其結果，可採用現有的冷凍機以代替專為低溫泵10設計之冷凍機。其有助於降低低溫泵10的製造成本。
另外，為了在低溫泵中心軸C將第2段低溫板組件20進行定位，低溫板定位構件67的上邊部67a可以與圖1所示相反地，從第2冷卻台24的凸緣部24a沿冷凍機16的中心軸D的方向遠離第2缸體25之方式延伸。對於具有大口徑的進氣口12之低溫泵10而言，具有該種形狀之低溫板定位構件67為適當。
低溫泵10具備以使從屏蔽件主開口34流入之氣體的流向從冷凍機結構部21偏向的方式構成之氣體流向調整構件50。氣體流向調整構件50以使通過入口低溫板32或開放區域48而流入主收容空間65之氣體流向從第2缸體25偏向之方式構成。氣體流向調整構件50可以是在冷凍機結構部21或第2缸體25的上方與之相鄰配置之氣體流向偏向構件或氣體流向反射構件。氣體流向調整構件50局部設置於周向上與屏蔽件側部開口44相同的位置。氣體流向調整構件50自上觀察時為矩形形狀。氣體流向調整構件50例如為一片平坦板，亦可以彎曲。
氣體流向調整構件50從屏蔽件側部40延伸，且插入於間隙區域66。但是，氣體流向調整構件50不與頂部低溫板60、第2缸體25及包圍其他間隙區域66之第2冷卻溫度的部位接觸。氣體流向調整構件50經由放射屏蔽件30熱耦合於第1冷卻台22。因此，氣體流向調整構件50被冷卻為第1冷卻溫度。
低溫泵殼體70為收容第1段低溫板18、第2段低溫板組件20及冷凍機16之低溫泵10的筐體，其為以保持內部空間14的真空氣密的方式構成之真空容器。低溫泵殼體70以非接觸之方式包括第1段低溫板18及冷凍機結構部21。低溫泵殼體70安裝於冷凍機16的室溫部26。
藉由低溫泵殼體70的前端，進氣口12被分隔。低溫泵殼體70具備從其前端朝向徑向外側延伸之進氣口凸緣72。進氣口凸緣72遍及低溫泵殼體70的全周而設置。低溫泵10使用進氣口凸緣72而安裝於真空排氣對象的真空腔室。
低溫泵殼體70具備以與放射屏蔽件30非接觸之方式包圍放射屏蔽件30之低溫板收容部76及包圍冷凍機16的第1缸體23之冷凍機收容部77。低溫板收容部76與冷凍機收容部77形成為一體。
低溫板收容部76在一端形成有進氣口凸緣72，另一端具有作為殼體底面70a而封閉之圓筒狀或圓頂狀的形狀。在將進氣口凸緣72連接於殼體底面70a之低溫板收容部76的側壁與進氣口12獨立形成有插穿冷凍機16之開口。冷凍機收容部77具有從該開口向冷凍機16的室溫部26延伸之圓筒狀的形狀。冷凍機收容部77將低溫板收容部76連接於冷凍機16的室溫部26。
低溫泵10具備安裝於低溫泵殼體70的外側之吸水層80及配置於低溫泵殼體70與吸水層80之間之隔熱層82。低溫泵10的結露抑制結構由吸水層80及隔熱層82形成。結露抑制結構具備在外側具有吸水層80且在內側具有隔熱層82之吸水隔熱片84。吸水隔熱片84作為在隔熱層82的外側貼合吸水層80而成之片材而構成。
吸水隔熱片84覆蓋低溫泵殼體70的外表面的至少一部分，例如整個面。吸水隔熱片84安裝於低溫板收容部76和冷凍機收容部77中兩處，且覆蓋該等的大致整個面。吸水隔熱片84纏繞於低溫板收容部76的側面，且覆蓋該側面。又，吸水隔熱片84亦安裝於殼體底面76a。吸水隔熱片84亦纏繞於冷凍機收容部77。吸水隔熱片84利用適當的黏著方法安裝於低溫泵殼體70。
但是，進氣口凸緣72未被吸水隔熱片84覆蓋。一般情況下，進氣口凸緣72即使露出亦不產生結露，因此無需將吸水層80及/或隔熱層82安裝於進氣口凸緣72。另外，必要情況下，吸水層80及/或隔熱層82可以安裝於進氣口凸緣72。
吸水層80與形成低溫泵殼體70的外表面之構成材料(例如，SUS304等不鏽鋼)及/或與形成隔熱層82之隔熱材料相比由吸水性優異的材料形成。吸水層80例如由吸水性樹脂、吸水性多孔質材料等化學性及/或物理性地吸附水分之吸水材料或含有這種吸水材料之材料形成。吸水層80能夠適當採用以吸水性樹脂、吸水聚合物、吸水片等一般名稱市售之商品。或者，吸水層80可以由毛氈、海綿等至少暫時保持水分之材料形成。
隔熱層82由與形成低溫泵殼體70的外表面之構成材料相比導熱率小的材料形成。隔熱層82例如可以由發泡系隔熱材及/或纖維系隔熱材等各種公知的隔熱材料形成。
隔熱層82的厚度86被設定為，吸水層80的溫度在低溫泵10再生期間，維持高於0℃的溫度。隔熱層82的厚度86可以被設定為，吸水層80的溫度維持高於5℃或高於10℃的溫度。換言之，隔熱層82的厚度86被設定為，在低溫泵10再生期間，隔熱層82的外表面的溫度不低於水的凝固點。
以下對上述結構的低溫泵10的動作進行說明。低溫泵10在工作時，首先在該工作之前用其他適當的粗抽泵將真空腔室內部粗抽至1Pa左右。之後，使低溫泵10工作。藉由冷凍機16的驅動，第1冷卻台22及第2冷卻台24分別被冷卻為第1冷卻溫度及第2冷卻溫度。藉此，熱耦合於該等之第1段低溫板18、第2段低溫板組件20亦分別被冷卻為第1冷卻溫度及第2冷卻溫度。
入口低溫板32對從真空腔室朝向低溫泵10飛來之氣體進行冷卻。藉由第1冷卻溫度而蒸氣壓充分低的(例如10-8
Pa以下的)氣體凝結在入口低溫板32的表面。該氣體可以稱為第1種氣體(亦稱為1類氣體)。第1種氣體例如為水蒸氣。如此，入口低溫板32能夠排出第1種氣體。藉由第1冷卻溫度而蒸氣壓未充分變低的氣體的一部分通過入口低溫板32或開放區域48而進入至主收容空間65。或者，氣體的另一部分被入口低溫板32反射而不進入到主收容空間65。
進入到主收容空間65之氣體藉由第2段低溫板組件20被冷卻。藉由第2冷卻溫度而蒸氣壓充分低的(例如10-8
Pa以下的)氣體凝結在第2段低溫板組件20的表面。該氣體可以稱為第2種氣體(亦稱為2類氣體)。第2種氣體例如為氮氣、氬氣。如此，第2段低溫板組件20能夠排出第2種氣體。因直接面向主收容空間65，因此在頂部低溫板60的前表面，第2種氣體的凝結層可能會大幅成長。另外，第2種氣體為藉由第1冷卻溫度不會凝結的氣體。
藉由第2冷卻溫度而蒸氣壓未充分變低的氣體被第2段低溫板組件20的吸附材74吸附。該氣體可以稱為第3種氣體(亦稱為3類氣體)。第3種氣體例如為氫氣。如此，第2段低溫板組件20能夠排出第3種氣體。因此，低溫泵10藉由凝結或吸附來排出各種氣體，藉此能夠使真空腔室的真空度達到所希望的級別。
藉由排氣運轉的連續，氣體逐漸蓄積在低溫泵10。為了向外部排出所蓄積之氣體，而進行低溫泵10的再生。若再生結束，則能夠再次開始排氣運轉。
為了促進低溫泵10的升溫並縮短再生時間，通常在開始再生的同時向低溫泵殼體70內導入沖洗氣體。藉由沖洗氣體和積存之氣體的再次氣化，低溫泵殼體70內充滿氣體，因此，與排氣運轉期間不同，真空隔熱效果消失。經由氣體而促進低溫板與低溫泵殼體70的熱交換。剛開始再生時，低溫板還保持極低溫，因此低溫泵殼體70能夠被冷卻。
又，低溫泵10的主收容空間65較寬，因此能夠積存大量的第2種氣體。在再生的比較初始階段，第2種氣體溶解為液體。如上所述，第2種氣體為氮氣或氬氣等，因此該液化氣體非常涼。液化氣體流至放射屏蔽件30或低溫泵殼體70的底部，且能夠與低溫泵殼體70的內表面接觸。如此一來，低溫泵殼體70被顯著冷卻。因此，周圍空氣中的水分有可能在低溫泵殼體70的外表面結露或附著霜。再生期間，低溫泵10逐漸向升溫至室溫，霜不久就會溶解。若附著大量的霜，則因該霜溶解而成為大量的水而有可能滴落。有可能弄濕低溫泵10周圍的其他裝置和物品或地面。
實施形態之低溫泵10具備安裝於低溫泵殼體70的外側之吸水層80。欲附著於低溫泵殼體70的外表面之水分被吸水層80吸收。因此，能夠抑制對低溫泵10的結露。結露得到抑制，因此對低溫泵10周圍和地面的水的滴落亦得到抑制。
又，隔熱層82配置於低溫泵殼體70與吸水層80之間。與低溫泵殼體70的溫度下降相比，隔熱層82的外表面的溫度下降變小。與不經由隔熱層82而由吸水層80直接安裝於低溫泵殼體70之情況相比，能夠縮小外部氣溫與吸水層80之間的溫差。藉此，能夠抑制對低溫泵10的結露。
若隔熱層82的外表面溫度低於室溫，則有可能產生結露。為了不設置吸水層80而僅藉由隔熱層82來防止結露，必須將隔熱層82的厚度86設定地足夠厚。此時，所需的隔熱層82的厚度86有可能厚到實際難以安裝到低溫泵殼體70。
但是，實施形態之低溫泵10具有吸水層80，因此能夠吸收有可能在隔熱層82的外表面結露之水分。隔熱層82的外表面可以比室溫稍微低，而能夠將隔熱層82設定得薄。推測為吸水層80本身的厚度無需那麼厚。因此，藉由組合吸水層80與隔熱層82，能夠作為整體實現厚度小的結露抑制結構，更便於安裝到低溫泵10。
一種典型的以往的低溫泵，其為了抑制結露，帶式加熱器等電加熱器而纏繞在殼體。實施形態之低溫泵10還具有無需這種電加熱器之優點(藉此，實施形態之低溫泵10不具有對低溫泵殼體70進行加熱之電加熱器)。
又，實施形態之低溫泵10亦不需要亦稱為排水盤之接水槽。
低溫泵10具備在外側具有吸水層80且在內側具有隔熱層82之吸水隔熱片84。吸水層80與隔熱層82為獨立的層時，需要進行首先在低溫泵殼體70安裝隔熱層82，其次在隔熱層82安裝吸水層80之兩個步驟的作業。為吸水隔熱片84時，能夠將吸水層80和隔熱層82一起安裝到低溫泵殼體70，因此便於製造。
假設吸水層80的外表面溫度低於0℃，則結露之水分有可能在吸水層80的外表面上結冰。冰層從吸水層80分離而附著於吸水層80上。藉由低溫泵10的升溫而冰層溶解時，有可能水會滴落。但是，依實施形態，隔熱層82的厚度86被設定為吸水層80的溫度在低溫泵10的再生期間維持高於0℃的溫度。因此，對吸水層80上的冰層形成得到抑制，水的滴落亦得到抑制。
以上，依據實施例對本發明進行了說明。所屬技術領域中具有通常知識者當然能夠理解本發明並不限定於上述實施形態，且能夠進行各種設計變更而且存在各種變形例，並且這種變形例亦屬於本發明的範圍。
上述實施形態中，吸水隔熱片84安裝於低溫板收容部76和冷凍機收容部77這兩處，但並不是必須的。吸水層80、隔熱層82及/或吸水隔熱片84可以僅安裝於低溫板收容部76與冷凍機收容部77中的任一個上。
吸水層80、隔熱層82及/或吸水隔熱片84可以以僅覆蓋低溫泵殼體70的外表面的一部分之方式安裝於低溫泵殼體70。例如，吸水隔熱片84可以僅安裝於低溫板收容部76的下部。如此一來，能夠藉由吸水隔熱片84來吸收從低溫板收容部76的上部流下來之結露而抑制結露的滴落。又，有時在冷凍機收容部77具備閥或感測器等從筒狀部向外側突出之構成要素。這種構成要素可以不被吸水隔熱片84覆蓋。
吸水層80可以配置於低溫泵殼體70與隔熱層82之間。亦即，吸水層80可以配置於隔熱層82的內側。例如，如圖3所示，低溫泵殼體70能夠具有角部或彎曲部。為了提供良好的隔熱性，隔熱層82的厚度86比較大。因此，還考慮到隔熱層82不易緊貼於角部或彎曲部，難以完全覆蓋的情況。這種情況下，如圖示，可以藉由吸水層80覆蓋低溫泵殼體70的角部或彎曲部。
又，如圖4所示，隔熱層82難以完全覆蓋低溫泵殼體70的角部或彎曲部時，吸水層80可以從外側覆蓋隔熱層82。此時，在低溫泵殼體70的角部或彎曲部未設置有隔熱層82，因此可以在角部或彎曲部與吸水層80之間形成有間隙87。
如圖5所示，低溫泵10可以具備排水盤88。排水盤88作為配置於低溫泵殼體70的下方之接水槽而設置，且以防止結露水滴落到地面94及/或接收存儲滴落之結露水之方式構成。排水盤88安裝於低溫泵殼體70的低溫板收容部76。排水盤88可以與腳輪90一起緊固在低溫板收容部76。隔熱墊片92可以插入於排水盤88與低溫板收容部76之間。另外，排水盤88可以藉由從進氣口凸緣72懸架等其他方法安裝於低溫泵殼體70。
吸水層80、隔熱層82及/或吸水隔熱片84安裝於冷凍機收容部77。吸水層80、隔熱層82及/或吸水隔熱片84可以安裝於低溫板收容部76。如此，作為實施形態之結露抑制結構可以併用排水盤88。
上述說明中例示出臥式低溫泵，但本發明亦能夠應用於立式等其他低溫泵。另外，立式低溫泵是指冷凍機16沿低溫泵10的低溫泵中心軸C配設之低溫泵。此時，冷凍機收容部77設置於殼體底面76a而非低溫板收容部76的側面。又，低溫板的配置和形狀、數量等低溫泵的內部結構並不限於上述特定實施形態。能夠適當採用各種公知的結構。Hereinafter, the mode for implementing the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent constituent elements, members, and processing are designated with the same symbols, and repeated descriptions are appropriately omitted. The scales and shapes of the depicted parts are simply set for ease of explanation, and unless otherwise specified, they are interpreted as non-limiting. The embodiment is an example and does not limit the scope of the present invention in any way. All the features and combinations described in the embodiments are not necessarily the essence of the invention. Fig. 1 is a side sectional view schematically showing the cryopump 10 of the embodiment. Fig. 2 is a schematic cross-sectional view taken along the line AA of the cryopump 10 shown in Fig. 1. Figure 1 shows a cross section including the central axis C of the cryopump indicated by a chain line. However, for ease of understanding, FIG. 1 shows the side surface of the cryopump 10 and the refrigerator instead of the cross section. As described later, the cryopump 10 has a condensation suppression structure. The cryopump 10 is used to increase the vacuum chamber installed in, for example, an ion implantation device, a sputtering device, an evaporation device, or other vacuum processing devices, and to increase the degree of vacuum inside the vacuum chamber to the level required for the desired vacuum processing. use. The cryopump 10 has an air inlet 12 for receiving the exhaust from the vacuum chamber. The gas enters the internal space 14 of the cryopump 10 through the air inlet 12. The cryopump 10 can be installed in a vacuum chamber with the orientation of the drawing, that is, the air inlet 12 facing upward. However, the posture of the cryopump 10 is not limited to this, and the cryopump 10 may be installed in the vacuum chamber in other orientations. In addition, in the following, in order to clearly express the positional relationship of the components of the cryopump 10, terms such as "axial direction" and "radial direction" may be used. The axial direction indicates the direction passing through the air inlet 12 (in FIG. 1, the direction along the central axis C of the cryopump passing through the center of the air inlet 12), and the radial direction indicates the direction along the air inlet 12 (vertical to the central axis C). direction). For convenience, sometimes with regard to the axial direction, it is called "up" when it is relatively close to the air inlet 12, and it is called "down" when it is relatively far away. That is, sometimes the bottom of the cryopump 10 that is relatively far away is referred to as "upper", and that it is relatively close is referred to as "down". Regarding the radial direction, the center near the intake port 12 (the center axis C in FIG. 1) is called "inner", and the periphery near the intake port 12 is called "outer". In addition, this form of expression has nothing to do with the configuration of the cryopump 10 when it is installed in the vacuum chamber. For example, the cryopump 10 may be installed in the vacuum chamber with the air inlet 12 facing downward in the vertical direction. In addition, the direction surrounding the axial direction is sometimes referred to as the "circumferential direction". The circumferential direction is the second direction along the intake port 12 and is a tangential direction perpendicular to the radial direction. The cryopump 10 includes a refrigerator 16, a first-stage cryogenic plate 18, a second-stage cryogenic plate assembly 20, and a cryopump casing 70. The first-stage low temperature plate 18 may also be referred to as a high temperature and low temperature plate portion or a 100K portion. The second-stage cryogenic plate assembly 20 may also be referred to as a cryogenic plate portion or a 10K portion. The refrigerator 16 is, for example, an extremely low temperature refrigerator such as a Gifford-McMahon refrigerator (so-called GM refrigerator). The refrigerator 16 is a two-stage refrigerator. Therefore, the refrigerator 16 includes a first cooling stage 22 and a second cooling stage 24. The refrigerator 16 is configured to cool the first cooling stage 22 to the first cooling temperature and to cool the second cooling stage 24 to the second cooling temperature. The second cooling temperature is a temperature lower than the first cooling temperature. For example, the first cooling stage 22 is cooled to about 65K to 120K, preferably 80K to 100K, and the second cooling stage 24 is cooled to about 10K to 20K. In addition, the refrigerator 16 includes a refrigerator structure 21 in which the second cooling stage 24 is structurally supported by the first cooling stage 22 and the first cooling stage 22 is structurally supported by the room temperature part 26 of the refrigerator 16. Therefore, the refrigerator structure 21 includes a first cylinder 23 and a second cylinder 25 that extend coaxially in the radial direction. The first cylinder 23 connects the room temperature part 26 of the refrigerator 16 to the first cooling stage 22. The second cylinder block 25 connects the first cooling stage 22 to the second cooling stage 24. The room temperature part 26, the first cylinder 23, the first cooling stage 22, the second cylinder 25, and the second cooling stage 24 are arranged in a straight line in this order. Each of the first cylinder 23 and the second cylinder 25 is provided with a first displacer and a second displacer (not shown) capable of reciprocating movement. A first cold accumulator and a second cold accumulator (not shown) are assembled in the first displacer and the second displacer, respectively. In addition, the room temperature part 26 has a drive mechanism (not shown) for reciprocating the first displacer and the second displacer. The driving mechanism includes a flow path switching mechanism that switches the flow path of the working gas in such a way that the working gas (for example, helium) is periodically and repeatedly supplied and discharged into the inside of the refrigerator 16. The first cooling stage 22 is installed at the low temperature end of the first stage of the refrigerator 16. The first cooling stage 22 is a member that surrounds the end of the first cylinder 23 from the outside on the side opposite to the room temperature portion 26 and surrounds the first expansion space of the working gas. The first expansion space is a variable volume formed between the first cylinder 23 and the first displacer in the inside of the first cylinder 23, and the volume changes with the reciprocating movement of the first displacer. The first cooling stage 22 is formed of a metal material having a higher thermal conductivity than the first cylinder block 23. For example, the first cooling stage 22 is formed of copper, and the first cylinder block 23 is formed of stainless steel. The second cooling stage 24 is installed at the second stage low-temperature end of the refrigerator 16. The second cooling stage 24 is a member that surrounds the end of the second cylinder 25 from the outside on the side opposite to the room temperature portion 26 and surrounds the second expansion space of the working gas. The second expansion space is a variable volume formed between the second cylinder 25 and the second displacer in the inside of the second cylinder 25, and the volume changes with the reciprocating movement of the second displacer. The second cooling stage 24 is formed of a metal material having a higher thermal conductivity than the second cylinder 25. The second cooling stage 24 is formed of copper, and the second cylinder block 25 is formed of stainless steel. FIG. 1 shows the boundary 24b between the second cooling stage 24 and the second cylinder block 25. The refrigerator 16 is connected to a compressor (not shown) for working gas. The refrigerator 16 expands the working gas pressurized by the compressor to cool the first cooling stage 22 and the second cooling stage 24. The expanded working gas is recovered to the compressor to be pressurized again. The refrigerator 16 generates cold by the repetition of a heat cycle including the supply and discharge of working gas and the reciprocating movement of the first displacer and the second displacer in synchronization with it. The cryopump 10 shown in the figure is a so-called horizontal cryopump. The horizontal cryopump generally refers to a cryopump in which the refrigerator 16 is arranged to cross the central axis C of the cryopump 10 (usually orthogonal). The first cooling stage 22 and the second cooling stage 24 of the refrigerator 16 are arranged in a direction perpendicular to the cryopump central axis C (horizontal direction in FIG. 1 and the direction of the central axis D of the refrigerator 16). The first-stage cryogenic plate 18 includes a radiation shield 30 and an entrance cryogenic plate 32, and surrounds the second-stage cryogenic plate assembly 20. The first-stage cryogenic plate 18 is a cryogenic plate for protecting the second-stage cryogenic plate assembly 20 from radiant heat from the outside of the cryopump 10 or the cryopump housing 70. The first-stage cryoplate 18 is thermally coupled to the first cooling stage 22. Thereby, the first-stage cryogenic plate 18 is cooled to the first cooling temperature. The first-stage cryogenic plate 18 has a gap with the second-stage cryogenic plate assembly 20, and the first-stage cryogenic plate 18 does not contact the second-stage cryogenic plate assembly 20. The radiation shield 30 is provided to protect the second-stage cryoplate assembly 20 from radiant heat from the cryopump housing 70. The radiation shield 30 is located between the cryopump housing 70 and the second-stage cryogenic plate assembly 20 and surrounds the second-stage cryogenic plate assembly 20. The radiation shield 30 has a shield main opening 34 for receiving gas from the outside of the cryopump 10 to the internal space 14. The main opening 34 of the shield is located at the air inlet 12. The radiation shield 30 includes: a front end 36 of the shield, which defines the main opening 34 of the shield; a bottom 38 of the shield, located on the side opposite to the main opening 34 of the shield; and a side part 40 of the shield, which connects the front end 36 of the shield to the shield Pieces at the bottom 38. The front end 36 of the shield constitutes a part of the side 40 of the shield. The shield side portion 40 extends in the axial direction from the shield front end 36 to the side opposite to the shield main opening 34, and extends so as to surround the second cooling stage 24 in the circumferential direction. The radiation shield 30 has the shape of a cylinder (for example, a cylinder) with the bottom 38 of the shield closed, and is formed in a cup shape. An annular gap 42 is formed between the side portion of the shield 40 and the second-stage cryogenic plate assembly 20. In addition, the shield bottom 38 may be a separate member from the shield side 40. For example, the bottom 38 of the shield may be a flat disk with approximately the same diameter as the side 40 of the shield, or it may be mounted on the side 40 of the shield on the side opposite to the main opening 34 of the shield. In addition, at least a part of the bottom 38 of the shield may be opened. For example, the radiation shield 30 may not be closed by the bottom 38 of the shield. That is, the shield side portion 40 may be opened at both ends. The shield side 40 has a shield side opening 44 into which the refrigerator structure 21 is inserted. The second cooling stage 24 and the second cylinder block 25 are inserted into the radiation shield 30 from the outside of the radiation shield 30 through the shield side opening 44. The side opening 44 of the shield is a mounting hole formed in the side 40 of the shield, for example, a circular shape. The first cooling stage 22 is arranged outside the radiation shield 30. The shield side portion 40 is provided with a mounting seat 46 of the refrigerator 16. The mounting seat 46 is a flat portion for mounting the first cooling stage 22 to the radiation shield 30 and is slightly recessed when viewed from the outside of the radiation shield 30. The mounting seat 46 forms the outer periphery of the side opening 44 of the shield. The mounting seat 46 is closer to the bottom 38 of the shield than the front end 36 of the shield in the axial direction. The first cooling stage 22 is mounted on the mounting base 46, whereby the radiation shield 30 is thermally coupled to the first cooling stage 22. The inlet cryoplate 32 is provided in the shield main opening 34 in order to protect the second-stage cryoplate assembly 20 from radiant heat from a heat source outside the cryopump 10. The heat source outside the cryopump 10 is, for example, a heat source in the vacuum chamber where the cryopump 10 is installed. In addition to radiant heat, the inlet cryoplate 32 can restrict the entry of gas molecules. The inlet cryoplate 32 occupies a part of the opening area of the main opening 34 of the shield to restrict the gas flowing into the internal space 14 through the main opening 34 of the shield to a desired amount. An annular open area 48 is formed between the inlet cryoplate 32 and the front end 36 of the shield. The entrance cryoplate 32 is installed at the front end 36 of the shielding member by an appropriate mounting member, and is thermally coupled to the radiation shielding member 30. The entrance cryoplate 32 is thermally coupled to the first cooling stage 22 via the radiation shield 30. The inlet cryopanel 32 has, for example, a plurality of ring-shaped or linear louvers. Alternatively, the inlet cryoplate 32 may be a sheet-like member. The second-stage cryogenic plate assembly 20 is mounted on the second cooling stage 24 so as to surround the second cooling stage 24. Thereby, the second-stage low-temperature plate assembly 20 is thermally coupled to the second cooling stage 24, and the second-stage low-temperature plate assembly 20 is cooled to the second cooling temperature. The second-stage cryogenic plate assembly 20 is surrounded by the shield side portion 40 together with the second cooling stage 24. The second stage cryogenic plate assembly 20 includes a top cryogenic plate 60 opposite to the main opening 34 of the shield, a plurality of (two in this example) cryogenic plate members 62 and a cryogenic plate mounting member 64. Moreover, as shown in FIG. 1, the cryopump 10 includes a cryoplate positioning member 67. The heat-conducting part for thermally coupling the second-stage cryogenic plate assembly 20 to the second cooling stage 24 includes a cryogenic plate mounting member 64 and a cryogenic plate positioning member 67. The top cryogenic plate 60 and the cryogenic plate member 62 are attached to the second cooling stage 24 via the cryogenic plate mounting member 64 and the cryogenic plate positioning member 67. An annular gap 42 is formed between the top cryogenic plate 60 and the cryogenic plate member 62 and the shield side 40, so neither the top cryogenic plate 60 and the cryogenic plate member 62 are in contact with the radiation shield 30. The cryogenic plate member 62 is covered by the top cryogenic plate 60. The top cryogenic plate 60 is the part of the second-stage cryogenic plate assembly 20 that is closest to the inlet cryogenic plate 32. The top cryogenic plate 60 is arranged between the main opening 34 of the shield or the inlet cryogenic plate 32 and the refrigerator 16 in the axial direction. The top cryogenic plate 60 is located at the center of the internal space 14 of the cryopump 10 in the axial direction. Therefore, the main accommodating space 65 of the condensation layer is formed wider between the front surface of the top cryogenic plate 60 and the inlet cryogenic plate 32. The main storage space 65 of the condensed layer occupies the upper half of the internal space 14. The top cryogenic plate 60 is a substantially flat cryogenic plate vertically arranged in the axial direction. That is, the top cryogenic plate 60 extends in the radial direction and the circumferential direction. As shown in FIG. 2, the top cryogenic plate 60 is a circular plate-shaped panel having a larger size (for example, a projected area) than the entrance cryogenic plate 32. However, the size relationship between the top cryogenic plate 60 and the inlet cryogenic plate 32 is not limited to this, and the top cryogenic plate 60 may be smaller, or the two may have substantially the same size. The top cryogenic plate 60 is arranged so as to form a gap area 66 with the refrigerator structure 21. The gap region 66 is a blank portion formed in the axial direction between the back surface of the top cryogenic plate 60 and the second cylinder block 25. The cryoplate member 62 is provided with an adsorbent 74 such as activated carbon. The adsorption material 74 is adhered to the back surface of the cryogenic plate member 62, for example. The front surface of the cryoplate member 62 functions as a condensation surface, and the back surface functions as an adsorption surface. An adsorption material 74 may be provided on the front surface of the cryogenic plate member 62. Similarly, the top cryogenic plate 60 may have an adsorbent 74 on its front surface and/or back surface. Alternatively, the top cryogenic plate 60 may not include the adsorption material 74. The two cryogenic plate members 62 are arranged on both sides of the second cooling stage 24 with the cryopump central axis C therebetween. The cryogenic plate member 62 is arranged along a plane perpendicular to the central axis C of the cryopump. For ease of understanding, the cryogenic plate member 62 and the cryogenic plate mounting member 64 are represented by dotted lines in FIG. 2. The two cryogenic plate members 62 are arranged at a height position between the upper end and the lower end of the second cooling stage 24 in the direction of the central axis C of the cryopump. The two cryoplate members 62 are arranged at the same height. The second cooling stage 24 is provided with a flange portion 24a at the end in the direction perpendicular to the cryopump central axis C (the direction of the central axis D of the refrigerator 16). The upper end and the lower end of the second cooling stage 24 in the direction of the cryopump central axis C are determined by the flange portion 24a. That is, the two cryogenic plate members 62 are arranged at a height position between the upper end and the lower end of the flange portion 24a of the second cooling stage 24 in the direction of the cryopump central axis C. The two cryoplate members 62 are provided as the same part. The two cryoplate members 62 have the same shape and are formed of the same material. The cryoplate member 62 has an arch shape, a half moon shape, or a semicircular shape. The cryopanel member 62 is formed of, for example, a metal material with high thermal conductivity such as copper, and may be coated with a plating layer such as nickel. As shown in FIG. 2, the cryogenic plate member 62 has a circular arc portion 78 and a chord 79. When viewed in the direction of the cryopump central axis C, the two cryogenic plate members 62 are arranged to be symmetrical to each other with the center line of the two (the central axis D of the refrigerator 16) as the symmetry axis. The arc portions 78 of the two cryogenic plate members 62 are located on the same circumference centered on the central axis C of the cryopump. In addition, each cryogenic plate member 62 has a shape that passes through the midpoint of the chord 79 (or the cryopump central axis C) and has a line-symmetrical shape with the line E perpendicular to the chord 79 as the axis of symmetry. As shown in FIG. 1, the cryopanel positioning member 67 is fixed to the flange portion 24 a of the second cooling stage 24 and is supported by the second cooling stage 24. The cryopanel positioning member 67 is formed in an upside-down L-shape. By using the low temperature plate positioning member 67, the restriction on the length of the refrigerator 16 in the direction of the central axis D is alleviated. Even if the flange portion 24a of the second cooling stage 24 is located at a position deviated from the center axis C of the cryopump to the center axis D of the refrigerator 16, it is possible to adjust the length of the upper edge portion 67a of the cryopump positioning member 67 The second stage cryoplate assembly 20 is positioned on the central axis C of the cryopump. As a result, the existing refrigerator can be used instead of the refrigerator specially designed for the cryopump 10. This helps reduce the manufacturing cost of the cryopump 10. In addition, in order to position the second-stage cryoplate assembly 20 on the cryopump central axis C, the upper edge portion 67a of the cryoplate positioning member 67 may be opposite to that shown in FIG. 1, along the flange portion 24a of the second cooling stage 24 The direction of the central axis D of the refrigerator 16 extends away from the second cylinder 25. For the cryopump 10 having the air inlet 12 with a large diameter, the cryoplate positioning member 67 having such a shape is suitable. The cryopump 10 includes a gas flow adjustment member 50 configured to deflect the flow of the gas flowing in from the shield main opening 34 from the refrigerator structure 21. The gas flow direction adjusting member 50 is configured such that the flow direction of the gas flowing into the main storage space 65 through the inlet cryoplate 32 or the open area 48 is deflected from the second cylinder 25. The gas flow direction adjusting member 50 may be a gas flow direction deflecting member or a gas flow direction reflecting member arranged adjacent to the refrigerating machine structure 21 or the second cylinder 25. The gas flow direction adjusting member 50 is partially arranged at the same position as the shield side opening 44 in the circumferential direction. The gas flow direction adjusting member 50 has a rectangular shape when viewed from above. The gas flow direction adjusting member 50 is, for example, a flat plate, which can also be bent. The gas flow direction adjusting member 50 extends from the side portion 40 of the shield and is inserted into the gap area 66. However, the gas flow direction adjusting member 50 does not contact the top cryogenic plate 60, the second cylinder block 25, and the second cooling temperature portion surrounding the other gap region 66. The gas flow direction adjusting member 50 is thermally coupled to the first cooling stage 22 via the radiation shield 30. Therefore, the gas flow direction adjusting member 50 is cooled to the first cooling temperature. The cryopump housing 70 is a housing that houses the cryopump 10 of the first-stage cryogenic plate 18, the second-stage cryogenic plate assembly 20, and the refrigerator 16, and is a vacuum container constructed to keep the internal space 14 vacuum tight. . The cryopump housing 70 includes the first-stage cryogenic plate 18 and the refrigerator structure 21 in a non-contact manner. The cryopump housing 70 is attached to the room temperature section 26 of the refrigerator 16. By the front end of the cryopump housing 70, the air inlet 12 is partitioned. The cryopump housing 70 includes an inlet flange 72 extending from the front end toward the radially outer side. The air inlet flange 72 is provided over the entire circumference of the cryopump housing 70. The cryopump 10 is installed in a vacuum chamber of a vacuum exhaust target using an air inlet flange 72. The cryopump housing 70 includes a cryopreservation portion 76 that surrounds the radiation shield 30 without contact with the radiation shield 30 and a refrigerator storage portion 77 that surrounds the first cylinder 23 of the refrigerator 16. The cryopanel accommodating part 76 and the refrigerator accommodating part 77 are formed integrally. The cryopanel accommodating portion 76 has an air inlet flange 72 formed at one end, and the other end has a cylindrical or dome-like shape closed as a bottom surface 70a of the housing. An opening for penetrating the refrigerator 16 is independently formed on the side wall of the low-temperature board accommodating portion 76 connecting the air inlet flange 72 to the bottom surface 70 a of the casing and the air inlet 12. The refrigerator accommodating part 77 has a cylindrical shape extending from the opening to the room temperature part 26 of the refrigerator 16. The refrigerator accommodating part 77 connects the low temperature plate accommodating part 76 to the room temperature part 26 of the refrigerator 16. The cryopump 10 includes a water absorption layer 80 installed on the outside of the cryopump casing 70 and a heat insulation layer 82 disposed between the cryopump casing 70 and the water absorption layer 80. The condensation suppression structure of the cryopump 10 is formed by the water absorption layer 80 and the heat insulation layer 82. The dew condensation suppression structure includes a water-absorbing and heat-insulating sheet 84 having a water-absorbing layer 80 on the outside and a heat-insulating layer 82 on the inside. The water-absorbing heat-insulating sheet 84 is configured as a sheet in which the water-absorbing layer 80 is bonded to the outside of the heat-insulating layer 82. The water absorption and heat insulation sheet 84 covers at least a part of the outer surface of the cryopump casing 70, for example, the entire surface. The water-absorbing and heat-insulating sheet 84 is installed in two places of the low-temperature board housing part 76 and the refrigerator housing part 77, and covers substantially the whole surface of these. The water-absorbing and heat-insulating sheet 84 is wound around the side surface of the cryopanel housing portion 76 and covers the side surface. In addition, the water absorption and heat insulation sheet 84 is also installed on the bottom surface 76a of the housing. The water-absorbing heat-insulating sheet 84 is also wound around the refrigerator housing 77. The water absorption heat insulation sheet 84 is attached to the cryopump housing 70 by an appropriate adhesive method. However, the air inlet flange 72 is not covered by the water-absorbing heat insulating sheet 84. In general, even if the air inlet flange 72 is exposed, no condensation occurs, so there is no need to install the water absorption layer 80 and/or the heat insulation layer 82 on the air inlet flange 72. In addition, if necessary, the water absorption layer 80 and/or the heat insulation layer 82 may be installed on the air inlet flange 72. The water absorption layer 80 and the constituent material (for example, stainless steel such as SUS304) forming the outer surface of the cryopump casing 70 and/or are formed of a material having superior water absorption compared with the heat insulation material forming the heat insulation layer 82. The water absorbing layer 80 is formed of, for example, a water absorbing material that chemically and/or physically adsorbs water, such as a water absorbing resin or a water absorbing porous material, or a material containing such a water absorbing material. The water-absorbent layer 80 can appropriately use products that are commercially available under general names such as water-absorbent resin, water-absorbent polymer, and water-absorbent sheet. Alternatively, the water-absorbing layer 80 may be formed of a material that at least temporarily retains moisture, such as felt or sponge. The heat insulation layer 82 is formed of a material having a lower thermal conductivity than the constituent material forming the outer surface of the cryopump casing 70. The heat insulation layer 82 can be formed of various well-known heat insulation materials, such as a foam type heat insulation material and/or a fiber type heat insulation material, for example. The thickness 86 of the heat insulation layer 82 is set such that the temperature of the water absorption layer 80 maintains a temperature higher than 0° C. during the regeneration of the cryopump 10. The thickness 86 of the heat insulation layer 82 can be set such that the temperature of the water absorption layer 80 is maintained at a temperature higher than 5°C or higher than 10°C. In other words, the thickness 86 of the thermal insulation layer 82 is set such that the temperature of the outer surface of the thermal insulation layer 82 is not lower than the freezing point of water during the regeneration of the cryopump 10. The operation of the cryopump 10 having the above-mentioned structure will be described below. When the cryopump 10 is in operation, first use other appropriate roughing pumps to roughly pump the inside of the vacuum chamber to about 1 Pa before the operation. After that, the cryopump 10 is operated. By the driving of the refrigerator 16, the first cooling stage 22 and the second cooling stage 24 are cooled to the first cooling temperature and the second cooling temperature, respectively. Thereby, the first-stage cryogenic plate 18 and the second-stage cryogenic plate assembly 20 that are thermally coupled to these are also cooled to the first cooling temperature and the second cooling temperature, respectively. The inlet cryogenic plate 32 cools the gas flying from the vacuum chamber toward the cryopump 10. Gas whose vapor pressure is sufficiently low (for example, 10 -8 Pa or less) due to the first cooling temperature is condensed on the surface of the inlet cryoplate 32. This gas can be referred to as a type 1 gas (also referred to as a type 1 gas). The first type of gas is, for example, water vapor. In this way, the inlet cryoplate 32 can discharge the first gas. A part of the gas whose vapor pressure is not sufficiently lowered by the first cooling temperature enters the main storage space 65 through the inlet cryoplate 32 or the open area 48. Alternatively, another part of the gas is reflected by the inlet cryoplate 32 and does not enter the main storage space 65. The gas entering the main containing space 65 is cooled by the second-stage cryoplate assembly 20. The gas whose vapor pressure is sufficiently low (for example, 10 -8 Pa or less) due to the second cooling temperature is condensed on the surface of the second-stage cryoplate assembly 20. This gas can be referred to as a type 2 gas (also referred to as a type 2 gas). The second gas is, for example, nitrogen gas and argon gas. In this way, the second-stage cryoplate assembly 20 can discharge the second gas. Since it directly faces the main containing space 65, the condensation layer of the second gas may grow substantially on the front surface of the top cryoplate 60. In addition, the second type of gas is a gas that does not condense at the first cooling temperature. The gas whose vapor pressure is not sufficiently lowered by the second cooling temperature is adsorbed by the adsorbing material 74 of the second-stage cryoplate assembly 20. This gas can be referred to as type 3 gas (also known as type 3 gas). The third gas is, for example, hydrogen. In this way, the second-stage cryoplate assembly 20 can discharge the third gas. Therefore, the cryopump 10 discharges various gases through condensation or adsorption, thereby enabling the vacuum degree of the vacuum chamber to reach a desired level. With the continuation of the exhaust operation, gas is gradually accumulated in the cryopump 10. In order to discharge the accumulated gas to the outside, the cryopump 10 is regenerated. When the regeneration ends, the exhaust operation can be restarted. In order to promote the temperature increase of the cryopump 10 and shorten the regeneration time, the flushing gas is usually introduced into the cryopump housing 70 at the same time as the regeneration is started. By re-vaporizing the flushing gas and the accumulated gas, the cryopump housing 70 is filled with gas. Therefore, unlike during the exhaust operation, the vacuum insulation effect disappears. The heat exchange between the cryoplate and the cryopump housing 70 is promoted via the gas. At the beginning of regeneration, the cryoplate is still kept at an extremely low temperature, so the cryopump housing 70 can be cooled. In addition, since the main storage space 65 of the cryopump 10 is relatively wide, a large amount of the second gas can be stored. In the relatively initial stage of regeneration, the second gas is dissolved into liquid. As mentioned above, the second type of gas is nitrogen, argon, etc., so the liquefied gas is very cool. The liquefied gas flows to the bottom of the radiation shield 30 or the cryopump housing 70 and can contact the inner surface of the cryopump housing 70. In this way, the cryopump housing 70 is significantly cooled. Therefore, there is a possibility that moisture in the surrounding air may condense or adhere to the outer surface of the cryopump housing 70. During regeneration, the cryopump 10 gradually warms up to room temperature, and the frost will dissolve soon. If a large amount of frost adheres, the frost may dissolve and become a large amount of water, which may drip. It is possible to wet other devices and objects around the cryopump 10 or the ground. The cryopump 10 of the embodiment includes a water absorption layer 80 attached to the outside of the cryopump casing 70. The moisture to be attached to the outer surface of the cryopump casing 70 is absorbed by the water absorption layer 80. Therefore, condensation on the cryopump 10 can be suppressed. Condensation is suppressed, so the dripping of water around the cryopump 10 and the ground is also suppressed. In addition, the heat insulation layer 82 is arranged between the cryopump casing 70 and the water absorption layer 80. Compared with the temperature drop of the cryopump casing 70, the temperature drop of the outer surface of the heat insulating layer 82 becomes smaller. Compared with the case where the water absorption layer 80 is directly attached to the cryopump housing 70 without passing through the heat insulation layer 82, the temperature difference between the outside air temperature and the water absorption layer 80 can be reduced. This can suppress condensation on the cryopump 10. If the temperature of the outer surface of the heat insulation layer 82 is lower than room temperature, condensation may occur. In order not to provide the water-absorbing layer 80 but to prevent condensation only by the heat-insulating layer 82, the thickness 86 of the heat-insulating layer 82 must be set sufficiently thick. At this time, the required thickness 86 of the heat insulation layer 82 may be so thick that it is actually difficult to install it in the cryopump housing 70. However, the cryopump 10 of the embodiment has a water absorbing layer 80, so it can absorb moisture that may condense on the outer surface of the heat insulating layer 82. The outer surface of the heat insulation layer 82 may be slightly lower than room temperature, and the heat insulation layer 82 can be set thinner. It is presumed that the thickness of the water-absorbing layer 80 itself does not need to be so thick. Therefore, by combining the water absorption layer 80 and the heat insulation layer 82, a condensation suppression structure with a small thickness can be realized as a whole, and it is easier to install to the cryopump 10. In a typical conventional cryopump, in order to suppress condensation, an electric heater such as a band heater is wound around the casing. The cryopump 10 of the embodiment also has the advantage of not requiring such an electric heater (therefore, the cryopump 10 of the embodiment does not have an electric heater for heating the cryopump housing 70). In addition, the cryopump 10 of the embodiment does not require a water receiving tank also called a drain pan. The cryopump 10 includes a water absorption and heat insulation sheet 84 having a water absorption layer 80 on the outside and a heat insulation layer 82 on the inside. When the water-absorbing layer 80 and the heat-insulating layer 82 are separate layers, it is necessary to first install the heat-insulating layer 82 on the cryopump housing 70, and then to install the water-absorbing layer 80 on the heat-insulating layer 82. In the case of the water-absorbing and heat-insulating sheet 84, the water-absorbing layer 80 and the heat-insulating layer 82 can be attached to the cryopump housing 70 together, so it is easy to manufacture. Assuming that the temperature of the outer surface of the water-absorbing layer 80 is lower than 0° C., dew condensation water may freeze on the outer surface of the water-absorbing layer 80. The ice layer is separated from the water-absorbing layer 80 and attached to the water-absorbing layer 80. When the ice layer is dissolved by the temperature rise of the cryopump 10, water may drip. However, according to the embodiment, the thickness 86 of the heat-insulating layer 82 is set so that the temperature of the water-absorbing layer 80 maintains a temperature higher than 0° C. during the regeneration of the cryopump 10. Therefore, the formation of the ice layer on the water absorption layer 80 is suppressed, and the dripping of water is also suppressed. Above, the present invention has been described based on the embodiments. Those with ordinary knowledge in the technical field can of course understand that the present invention is not limited to the above-mentioned embodiment, and various design changes can be made and various modifications exist, and such modifications also belong to the scope of the present invention. In the above-mentioned embodiment, the water-absorbing and heat-insulating sheet 84 is attached to both the low-temperature board housing portion 76 and the refrigerator housing portion 77, but it is not essential. The water-absorbing layer 80, the heat-insulating layer 82, and/or the water-absorbing and heat-insulating sheet 84 may be attached to only any one of the low-temperature board housing part 76 and the refrigerator housing part 77. The water absorption layer 80, the heat insulation layer 82, and/or the water absorption heat insulation sheet 84 may be attached to the cryopump casing 70 so as to cover only a part of the outer surface of the cryopump casing 70. For example, the water-absorbing and heat-insulating sheet 84 may be attached only to the lower part of the cryopanel housing part 76. In this way, the water-absorbent heat-insulating sheet 84 can absorb the condensation that flows down from the upper portion of the cryopanel housing portion 76, and can suppress the dripping of the condensation. In addition, the refrigerating machine accommodating portion 77 may include components such as valves and sensors that protrude outward from the cylindrical portion. Such constituent elements may not be covered by the water-absorbing and heat-insulating sheet 84. The water absorption layer 80 may be disposed between the cryopump housing 70 and the heat insulation layer 82. In other words, the water absorption layer 80 may be arranged inside the heat insulation layer 82. For example, as shown in FIG. 3, the cryopump housing 70 can have corners or bends. In order to provide good thermal insulation, the thickness 86 of the thermal insulation layer 82 is relatively large. Therefore, it is also considered that the heat-insulating layer 82 does not easily adhere to corners or curved parts, and is difficult to cover completely. In this case, as shown in the figure, the corners or curved portions of the cryopump casing 70 can be covered by the water absorption layer 80. Moreover, as shown in FIG. 4, when it is difficult for the heat insulation layer 82 to completely cover the corner|angular part or the curved part of the cryopump housing 70, the water absorption layer 80 may cover the heat insulation layer 82 from the outside. At this time, the corner portion or curved portion of the cryopump casing 70 is not provided with the heat insulating layer 82, and therefore, a gap 87 may be formed between the corner portion or curved portion and the water absorption layer 80. As shown in FIG. 5, the cryopump 10 may include a drain pan 88. The drain pan 88 is provided as a water receiving tank arranged below the cryopump housing 70, and is configured to prevent dew condensation water from falling onto the ground 94 and/or to receive and store the dew condensation water. The drain pan 88 is attached to the cryogenic plate accommodating portion 76 of the cryopump housing 70. The drain pan 88 can be fastened to the low temperature board accommodating part 76 together with the casters 90. The heat insulation gasket 92 can be inserted between the drain pan 88 and the low temperature board accommodating part 76. In addition, the drain pan 88 may be mounted to the cryopump housing 70 by other methods such as suspension from the air intake flange 72. The water absorption layer 80, the heat insulation layer 82 and/or the water absorption heat insulation sheet 84 are attached to the refrigerator housing 77. The water absorption layer 80, the heat insulation layer 82, and/or the water absorption heat insulation sheet 84 may be installed in the low temperature board storage portion 76. In this way, the drain pan 88 may be used in combination as the dew condensation suppression structure of the embodiment. The above description illustrates a horizontal cryopump, but the present invention can also be applied to other cryopumps such as vertical. In addition, the vertical cryopump refers to a cryopump in which the refrigerator 16 is arranged along the cryopump center axis C of the cryopump 10. At this time, the refrigerator accommodating portion 77 is provided on the bottom surface 76 a of the casing instead of on the side surface of the cryoplate accommodating portion 76. In addition, the internal structure of the cryopump, such as the arrangement, shape, and number of cryopanels, is not limited to the specific embodiment described above. Various well-known structures can be appropriately adopted.
10‧‧‧低溫泵
10‧‧‧Cryogenic Pump
12‧‧‧進氣口
12‧‧‧Air inlet
14‧‧‧內部空間
14‧‧‧Internal space
16‧‧‧冷凍機
16‧‧‧Freezer
18‧‧‧第1段低溫板
18‧‧‧Section 1 cryogenic plate
20‧‧‧第2段低溫板組件
20‧‧‧Section 2 cryogenic plate assembly
21‧‧‧冷凍機結構部
21‧‧‧Freezer Structure Department
22‧‧‧第1冷卻台
22‧‧‧The first cooling station
23‧‧‧第1缸體
23‧‧‧Cylinder 1
24‧‧‧第2冷卻台
24‧‧‧Second cooling table
24a‧‧‧凸緣部
24a‧‧‧Flange
24b‧‧‧界限
24b‧‧‧ boundary
25‧‧‧第2缸體
25‧‧‧Cylinder 2
26‧‧‧室溫部
26‧‧‧Room temperature
30‧‧‧放射屏蔽件
30‧‧‧Radiation shield
32‧‧‧入口低溫板
32‧‧‧Entrance cryogenic plate
34‧‧‧屏蔽件主開口
34‧‧‧Main opening of shield
36‧‧‧屏蔽件前端
36‧‧‧Front end of shield
38‧‧‧屏蔽件底部
38‧‧‧Bottom of shield
40‧‧‧屏蔽件側部
40‧‧‧Shield side
42‧‧‧環狀間隙
42‧‧‧Annular gap
44‧‧‧屏蔽件側部開口
44‧‧‧Shield side opening
46‧‧‧安裝座
46‧‧‧Mounting seat
48‧‧‧開放區域
48‧‧‧Open area
50‧‧‧氣體流向調整構件
50‧‧‧Gas flow direction adjustment component
60‧‧‧頂部低溫板
60‧‧‧Top low temperature board
62‧‧‧低溫板構件
62‧‧‧Cryogenic plate components
64‧‧‧低溫板安裝構件
64‧‧‧Cryogenic plate mounting components
65‧‧‧主收容空間
65‧‧‧Main containment space
66‧‧‧間隙區域
66‧‧‧Gap area
67‧‧‧低溫板定位構件
67‧‧‧Cryogenic plate positioning component
67a‧‧‧上邊部
67a‧‧‧Upper side
70‧‧‧低溫泵殼體
70‧‧‧Cryogenic pump housing
72‧‧‧進氣口凸緣
72‧‧‧Inlet flange
74‧‧‧吸附材
74‧‧‧Adsorption material
76‧‧‧低溫板收容部
76‧‧‧Cryogenic plate storage
76a‧‧‧殼體底面
76a‧‧‧Shell bottom
77‧‧‧冷凍機收容部
77‧‧‧Freezer Containment Department
80‧‧‧吸水層
80‧‧‧Water-absorbing layer
82‧‧‧隔熱層
82‧‧‧Insulation layer
84‧‧‧吸水隔熱片
84‧‧‧Water-absorbing insulation sheet
86‧‧‧厚度
86‧‧‧Thickness
C‧‧‧低溫泵中心軸
C‧‧‧Cryogenic pump central shaft
D‧‧‧中心軸
D‧‧‧Central axis
