JP4671153B2

JP4671153B2 - Open window ionization chamber

Info

Publication number: JP4671153B2
Application number: JP2006066824A
Authority: JP
Inventors: 光隆横山
Original assignee: 横山義隆
Priority date: 2006-03-11
Filing date: 2006-03-11
Publication date: 2011-04-13
Anticipated expiration: 2026-03-11
Also published as: JP2007240467A

Description

従来の薄膜窓型電離箱は入射窓の薄膜やグリッドによる入射放射線の吸収があり真の値を評価することができなかったが、本発明は入射窓に薄膜やグリッドがないので、入射放射線の真の値を測定し評価のできる電離箱である。 While conventional thin film window ionization chamber could not be evaluated true value has absorption of incident radiation by thin film or grid entrance window, since the present invention does not thin or grid entrance window, the incident radiation It is an ionization chamber that can measure and evaluate the true value of.

従来の電離箱は外部からの静電誘導による擾乱を回避するために、入射窓には薄膜またはグリッドでシールドが必要であった。そのために約５ｋｅＶ以下のＸ線、またはα線の吸収が避けられず、真の放射線の量を評価することは困難であった。In the conventional ionization chamber, in order to avoid disturbance due to electrostatic induction from the outside, the entrance window needs to be shielded with a thin film or a grid. For this reason, absorption of X-rays or α rays of about 5 keV or less is unavoidable, and it has been difficult to evaluate the amount of true radiation.

薄膜による入射放射線の減衰が無視できない場合には膜無しの開放窓型電離箱が望まれていた。しかし、現実には薄膜を無くすると外部からの静電誘導の影響は避けられず、電離電流を測定することは困難であった。When the attenuation of incident radiation by a thin film cannot be ignored, an open window ionization chamber without a film has been desired. However, reality is inevitable effect of the electrostatic induction from the outside when eliminating the thin film, it is difficult to measure the ionization current.

しかし、本発明のように薄膜またはグリッドを除外した開放窓型電離箱は入射窓から入る外部静電誘導を回避するために集電極をシールド効果のある高圧電極や補助電極の陰に退避させ、電離電流は電位勾配に沿って集電極に運ぶ方法でこれを解決した。本発明はα線測定の場合、空気中で発生したイオン対による電離電流は数ｃｍの距離を電界に乗せて運ぶ方式である。However, it retracts the collector electrode to the negative of the high voltage electrode and the auxiliary electrode with shielding effect for an open window ionization chamber excluding the thin film or grid to avoid external electrostatic induction entering from the entrance window as in the present invention This was solved by a method in which the ionization current was carried along the potential gradient to the collector electrode. The present invention in the case of α-ray measurement, the ionization current due to the ion pairs generated in the air is a method of carrying put the distance of several cm to the electric field.

本発明はイオン対を電界の方向に乗せ集電極に運び検出する方法なのでイオン対の再結合が無視できる。一方イオン対の収集効率は落ちるが、α線の存在する場所から数メートル離れていても発生したイオン対を空気流に乗せてグリッド電離箱に運び測定するＬＲＡＤ技術がある。
ＭａｃＡｒｔｈｕｒＤＷ，ＡｌｌａｎｄｅｒＫＳ，ＢｏｕｎｄｓＪＡ，ｅｔａｌ：Ｌｏｎｇ−ＲａｎｇｅＡｌｐｈａＤｅｔｅｃｔｏｒ（ＬＲＡＤ）ｆｏｒＣｏｎｔａｍｉｎａｔｉｏｎＭｏｎｉｔｏｒｉｎｇ：ＩＥＥＥＴｒａｎｓａｃｔｉｏｎｏｎＮｕｃｌｅａｒＳｃｉｅｎｃｅ，３９，Ｎｏ．４，ｐｐ９５２−９５７（１９９２） Since the present invention is a method in which the ion pair is carried in the direction of the electric field and carried to the collecting electrode, recombination of the ion pair can be ignored. On the other hand, although the ion pair collection efficiency is reduced, there is an LRAD technique in which an ion pair generated is carried on an air flow and carried to a grid ionization chamber even if it is several meters away from a place where α rays exist.
MacArthur DW, Alexander KS, Bounds JA, et al: Long-Range Alpha Detector (LRAD) for Continuation Monitoring: IEEE Transaction on Nuclear Science, 39. 4, pp952-957 (1992)

入射放射線により、空気または気体中に付与された真のイオン対の量を評価するために入射窓の薄膜またはグリッドを取り去り開放窓型電離箱とし、入射放射線の薄膜またはグリッドによる吸収を無くした。The incident radiation, and an open window ionization chamber removed and a thin film or grid entrance window to evaluate the amount of the true ion pair granted to air or gas, without absorption by thin film or grid of the incident radiation did.

入射窓の膜またはグリッドを無くしたことにより、外部からの静電誘導を受けないように集電極を配置する。 By eliminating the membrane or grid entrance window, placing the collector electrode so as not to undergo electrostatic induction from the outside.

入射窓の薄膜またはグリッドを無くしたことにより、外部からの静電誘導を受けないように集電極をシールド効果のある高圧電極、補助電極の陰に退避させた構造の電離箱とした。By eliminating the thin film or grid entrance window and the ionization chamber of the high-voltage electrode, it is retracted behind the auxiliary electrode structure collectors so not subject to electrostatic induction with the shielding effect of the external.

請求項６のα線測定用電離箱において、高圧電極と集電極の中間の補助電極は省略することもできる。 In the ionization chamber for α ray measurement according to claim 6, the auxiliary electrode in the middle of the high voltage electrode and the collector electrode can be omitted.

補助電極によりイオン対の再結合特性を改善したり、電気力線を変位させたり、あるいは電気力線を整合させたりすることができる。The auxiliary electrode can improve the recombination characteristics of the ion pair, displace the electric lines of force, or match the electric lines of force.

本発明による電離箱は薄膜またはグリッドによる入射放射線の吸収のない開放窓型電離箱なので、空気または気体中に付与された、真の全エネルギー量の測定が可能となる。Ionization chamber according to the invention since no absorption window opening ionization chamber of the incident radiation by thin film or grid, granted to air or gas, it is possible to measure the true total energy.

以下、本発明の好適な実施形態を図面に基づいて説明する。 DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

図１の集電極配置は単位体積中に発生したイオン対による電離電流を測定する場合の原理図で、高圧電極１、補助電極２、集電極３の電極間隔を同一にして抵抗Ｒにより分割接続した例である。The collector electrode arrangement in FIG. 1 is a principle diagram for measuring the ionization current due to ion pairs generated in a unit volume, and the electrode spacing of the high voltage electrode 1, auxiliary electrode 2 and collector electrode 3 is made the same and divided by a resistor R. This is an example.

図１の集電極３は反転増幅器に接続したとき仮想的にガード電極４と同電位になる。高圧電極１とガード電極４間に高圧を印加して電気力線が平行になるようにする。なお、シールドケース７は増幅器のグランド端子に接続し、ガード電極４と同電位にする。集電極３は高絶縁物５により支持され電離電流が出力される。補助電極２とガード電極４は絶縁物６を介して抵抗に接続されている。高圧電極１の支持絶縁物は省略してある。 The collector electrode 3 in FIG. 1 is virtually at the same potential as the guard electrode 4 when connected to an inverting amplifier. A high voltage is applied between the high voltage electrode 1 and the guard electrode 4 so that the lines of electric force are parallel. The shield case 7 is connected to the ground terminal of the amplifier and has the same potential as the guard electrode 4. The collector electrode 3 is supported by a high insulator 5 and outputs an ionization current. The auxiliary electrode 2 and the guard electrode 4 are connected to a resistor via an insulator 6. The supporting insulator for the high voltage electrode 1 is omitted.

図１において、高圧電極１とガード電極４間に高電圧を印加して電気力線が一様に平行になったとき、照射放射線ビームの断面積と補助電極の穴形状からイオン対の生じた実効体積が算出でき、これにより単位体積当たりの電離電流が算定できる電離箱。 In FIG. 1, when a high voltage is applied between the high-voltage electrode 1 and the guard electrode 4 and the lines of electric force are uniformly parallel, ion pairs are generated from the cross-sectional area of the irradiation radiation beam and the hole shape of the auxiliary electrode. An ionization chamber that can calculate the effective volume and the ionization current per unit volume.

図２は単位面積当たりのイオン対による電離電流測定の原理図である。集電極３は高圧電極１の陰に退避していて、入射窓からの静電誘導による擾乱を受けないように配慮されている。FIG. 2 is a principle diagram of ionization current measurement by ion pairs per unit area. The collecting electrode 3 is retracted behind the high-voltage electrode 1 and is considered not to be disturbed by electrostatic induction from the incident window.

図１の高圧電極１と補助電極２とガード電極４は抵抗ＲとＲにより、図２の高圧電極１と補助電極２とグランドは抵抗Ｒ１とＲ２により分割接続されている。集電極３は反転増幅器に接続したとき仮想接地となりグランドと同電位になる。高圧電極１とグランド間に高電圧を印加する。集電極は高絶縁物５（図２では省略）により支持され電離電流が出力される。図２では補助電極２は高圧電極１から絶縁物６を介して絶縁され、また別の絶縁物６を介して抵抗Ｒ１，Ｒ２に接続されている。The high-voltage electrode 1, auxiliary electrode 2 and guard electrode 4 in FIG. 1 are connected by resistors R and R, and the high-voltage electrode 1, auxiliary electrode 2 and ground in FIG. 2 are divided and connected by resistors R1 and R2. When the collector electrode 3 is connected to the inverting amplifier, it becomes a virtual ground and has the same potential as the ground. A high voltage is applied between the high voltage electrode 1 and the ground. The collector electrode is supported by a high insulator 5 (not shown in FIG. 2) and outputs an ionization current. In FIG. 2, the auxiliary electrode 2 is insulated from the high-voltage electrode 1 via an insulator 6 and is connected to resistors R 1 and R 2 via another insulator 6.

図２では窓から入射したα線により電離箱内で発生したイオン対による電離電流は補助電極２に向かう電界に乗って移動する。電離電流が集電極３の影響の及ぶ領域に入ると電界は補助電極２から集電極３に向かい急激に曲げられ、更にこれに乗って集電極３に運ばれる。これにより入射窓面積から単位面積当たりの電離電流が算定できる。In FIG. 2, the ionization current due to the ion pairs generated in the ionization chamber due to the α rays incident from the window moves on the electric field toward the auxiliary electrode 2. When the ionizing current enters the region affected by the collector electrode 3, the electric field is suddenly bent from the auxiliary electrode 2 toward the collector electrode 3, and further carried on the collector electrode 3. Thereby, the ionization current per unit area can be calculated from the incident window area .

本発明に係わる電離箱の集電極配置例で、単位体積当たりの放射線量を評価するときの図である。It is a figure when evaluating the radiation dose per unit volume in the collector electrode arrangement example of the ionization chamber according to the present invention. 本発明に係わる電離箱の集電極配置例で、これは単位面積当たりの放射線量を評価するときの図である。This is an example of the collector electrode arrangement of the ionization chamber according to the present invention, and is a diagram when evaluating the radiation dose per unit area.

Explanation of symbols

１高圧電極
２補助電極
３集電極
４ガード電極
５高絶縁物
６絶縁物
７シールドケース

1 High Voltage Electrode 2 Auxiliary Electrode 3 Collector Electrode 4 Guard Electrode 5 High Insulator 6 Insulator 7 Shield Case

Claims

The radiation entrance window with no window opening type of thin film or a grid, X-rays, or by that the absorption is avoided in the radiation entrance window of the α line, so as not to be affected by electrostatic induction entering through the entrance window from the outside, collecting high-voltage electrode in an electrode from the entrance window of by Uni shielding effect does not foresee direct, retracted behind the auxiliary electrode, and identifies the amount of ion pairs generated in the amount and per unit volume of radiation per unit area, the ionization current An ionization chamber with a structure that carries it to the collector electrode in the direction of the electric field.

Auxiliary electrode ionization chamber as claimed in claim 1, or displaces the electric lines of force, or Ri electrode der capable lines of electric force or aligned, further wherein the auxiliary electrode is disposed intermediate the high voltage electrode and the collecting electrode is, by applying a voltage between the electrodes, the ionization current ionization chamber which is to be transported to the collector electrode along the potential gradient.

Ionization chamber according to claim 1 that have a structure that can calculate the entrance window area when identifying the amount of radiation per unit area.

In claim 1 or claim 2 , the ionization chamber is a parallel plate type, a flat auxiliary electrode is disposed between the high voltage electrode and the collector electrode, and the center of the auxiliary electrode has a hole whose shape is easy to calculate , Hanarebako conductive structures ionization current per unit volume that can be calculated from the hole shape of the incident X-ray auxiliary electrode.

The ionization chamber according to claim 1 or claim 2 capable of measuring an ion pair concentration of the open window ionization chamber because the air or gas.

Α line surface contamination measuring ionization chamber using the ionization chamber of claim 3.

The ionization chamber of the ionization chamber according to claim 1 is an ionization chamber having a structure that is accommodated in a conductive shield case in order to prevent incident X-rays from being shielded and external electrostatic induction to the collector electrode.