SU714255A1

SU714255A1 - Device for measuring the lifetime and coefficient of capture of molecules

Info

Publication number: SU714255A1
Application number: SU782587845A
Authority: SU
Inventors: Анатолий Алексеевич Востриков; Юрий Семенович Куснер
Original assignee: Институт теплофизики СО АН СССР
Priority date: 1978-03-02
Filing date: 1978-03-02
Publication date: 1980-02-05

Description

Изобретение может быть испопьзовано дпя7. проведения исследований в области динамики разреженного газа, химфизики и криогенновакуумной техники/The invention may be used for 7. conducting research in the field of rarefied gas dynamics, chemical physics and cryogenic vacuum technology /

Известно измерение коэффициента захвата молекул путем направления молеку- , лярного пучка на исследуемую поверхность (мишень) и измерения интенсивности отражения пучка 14 ·It is known to measure the capture coefficient of molecules by directing the molecular beam to the surface under study (target) and measuring the intensity of reflection of the beam 14

Однако в этом случае требуется детек-_1втор большой чувствительности, который необходимо перемешать по полусфере.However, in this case, a high sensitivity detector ₁ is required, which must be mixed in a hemisphere.

Наиболее близким техническим решением к изобретению является устройство для измерения времени жизни коэффициент та захвата молекул на охлаждаемой поверхности, включающее источник молекулярного пучка, модулятор молекулярного пучка, исследуемую поверхность, на которую падает молекулярный пучок, иониза— _иционный детектор и избирательный усилитель [2] .The closest technical solution to the invention is a device for measuring the life time is the ratio of capture molecules on the cooling surface comprising a source of molecular beam modulator molecular beam test surface, onto which the molecular beam ionization detector _and insulating selective amplifier and [2].

Однакр эго устройство разового действия и сложно. ·However, the ego is a one-time device and complex. ·

Целью изобретения является упрощение измерений за счёт проведения их в небольших молекулярно-пучковых установках.The aim of the invention is to simplify measurements by conducting them in small molecular-beam installations.

Эта цель достигается тем, что в предложенном устройстве исследуемая поверхность (мишень) помешена внутри камеры торможения молекулярного пучка, совмещенной с ионизационным детектором и представляющей собой замкнутый объем с отверстием.This goal is achieved by the fact that in the proposed device, the investigated surface (target) is placed inside the braking chamber of the molecular beam, combined with an ionization detector and representing a closed volume with a hole.

На чертеже схематически изображено устройство, помещаемое в вакуумной камере.The drawing schematically shows a device placed in a vacuum chamber.

Оно состоит из камеры 1 торможения молекулярного пучка,фланца с отверстием для входа молекулярного пучка, фланца для крепления ионизационного детектора, блока с мишенью 4, температура которой может меняться с помощью хладагента, центрирующей мишень втулки 5, торцовой теплоизолирующей мембраны 6 и стойки 7 для крепления устройства ионизационного детектора 8.It consists of a molecular beam deceleration chamber 1, a flange with an opening for the entrance of the molecular beam, a flange for attaching an ionization detector, a unit with a target 4, the temperature of which can be changed with the help of a refrigerant, centering the target of the sleeve 5, a mechanical end-insulating membrane 6 and a stand 7 for mounting ionization detector devices 8.

i . - ......i. - ......

того, устройство содержит модулятор (на чертеже не испоКроме точник и казаны) молекулярного пучка, попадающего в камеру через отверстие во фланце.In addition, the device contains a modulator (not shown in the drawing also shows a cauldron) of a molecular beam entering the chamber through an opening in the flange.

Камера торможения представляет со$ой замкнутый объем с отверстием и совмещена с ионизационным детектором 8,The braking chamber represents a closed volume with a hole and is combined with an ionization detector 8,

Устройство работает следующим образом.The device operates as follows.

Модулированный молекулярный пучок через отверстие входит в камеру тормо' жения и падает нормально на исследуемую поверхность. Выходной сигнал иони’ запионнбго детектора пропорнионален Iппотности молекул в объеме камеры торможения и зависит от коэффициента захвата н времени жизни молекул на поверх-, носги. Изменяя температуру мишени и одновременно измеряя выходной сигнал де*·· тектора, можно получить зависимости времени жизни и коэффициента захвата молекул от температуры мишени. / . .A modulated molecular beam enters the braking chamber through an aperture and falls normally onto the surface under investigation. The output signal of the ion’s detector is proportional to the molecular weights in the volume of the drag chamber and depends on the capture coefficient and the lifetime of the molecules on the surface of the nose. By changing the temperature of the target and simultaneously measuring the output signal of the detector, it is possible to obtain the dependences of the lifetime and capture coefficient of molecules on the temperature of the target. /. .

Площадь отверстия 2 и площадь 6^ мишени должны отвечать следующему условию вцд -г Sg S /4ОО (где $ -общая внутренняя поверхность камеры торможения) для того, чтобы выходящий из отверстия 2 эффузионный поток был пропорционален, плотности и скорости молекул в объеме камеры торможения. Модулированный с частотой (fij молекулярный пучок входит в камеру через отверстие. Часть молекул эффундирует через отверстие, часть прилипает к исследуемой поверхности мишени. Результирующая плотность молекул в камере измеряется иони35The area of the hole 2 and the area 6 ^ of the target must meet the following condition: vdc-r Sg S / 4OO (where $ is the total internal surface of the braking chamber) so that the effusion flow coming out of the hole 2 is proportional to the density and velocity of molecules in the volume of the braking chamber . Modulated with frequency (fij, the molecular beam enters the chamber through the hole. Some of the molecules effound through the hole, some adhere to the target surface under study. The resulting molecular density in the chamber is measured by ion

..........

запионным детектором, сигнал которого, пропорциональный плотности молекул в камере, усиливается избирательным усилителем, настроенным на частоту (и .a zapion detector, whose signal, proportional to the density of molecules in the chamber, is amplified by a selective amplifier tuned to the frequency (and.

Изобретение позволяет значительно упростить исследования и использовать устройство в малогабаритных камерах.The invention can significantly simplify research and use the device in small cells.

Claims

. . . . -1:., The invention can be used FOR :, conducting research in the field of rarefied gas dynamics, physical physics and cryogenic-vacuum technology. It is known to measure the capture coefficient of molecules by directing the molecular beam at the surface under study (target) and measuring the intensity of the beam output 11. However, in this case, you need a high sensitivity detector that needs to be moved in a hemisphere. The closest technical solution to the invention is a device for measuring the lifetime of the coefficient. This includes the capture of molecules on a cooled surface, including the source of the molecular beam, the modulator of the molecular beam, the surface under investigation, on which the Mopecule beam falls, the ionization detector, and the selective amplifier. However, this is a one-time device and is difficult. The aim of the invention is to simplify measurements by conducting them in small molecular beam installations. This circuit is achieved by the fact that in the proposed device the test surface (target) is placed inside the deceleration chamber of the molecular beam, combined with the ionization detector and representing a closed volume with an obverse. The drawing shows schematically the device placed in a vacuum chamber. It consists of a molecular beam deceleration chamber 1, a flange with a hole 2d for the entrance of a molecular beam, a flange for mounting an ionization detector, a block with target 4, the temperature of which can be changed with the help of a refrigerant centering the sleeve 5, the end heat insulating membrane 6 and the stand 7 for mounting the ionization detector 8. 37 KpoNre, the device contains a source and a modulator (not shown in the drawing) of a molecular beam that enters the Kavfepy through an opening in the flange. The braking chamber is a closed volume with a hole and combined with an infrared detector (8, Set) and operates as follows. The modulated molecular beam of the Thunderbolt enters the stagnation chamber and falls normally on the test surface. The output signal of the ionisable ion detector is proportional to the density of molecules in the volume of the stagnation chamber and depends on the capture coefficient in the MololL life time on the surface. By varying the target temperature and simultaneously measuring the output signal of the detector, it is possible to obtain the dependences of the lifetime and coefficient of capture of molecules on the target temperature. The area of the hole 2 and the target S, y of the target must meet the following condition Sj -1- Sg S (where $ is the total inner surface of the stagnation chamber) so that the effusion flow leaving hole 2 is proportional to the density and velocity of the molecules in the volume of the braking chamber. The molecular beam modulated at a frequency Ou enters the chamber through the aperture. Some of the molecules effuse through the hole, and some adhere to the target surface being investigated. The resulting plottobtb molecules in the chamber are measured by an ionization detector f, the signal of which, proportional to the density of the molecules in the chamber, is amplified by a selective amplifier tuned to a frequency (O. The invention allows to simplify research and use the device in compact vacuum chambers. The invention formula for measurement of the lifetime and the coefficient of capture of molecules on a cooled surface, including the source of the molecular beam, mode | 1 torus of molecules) the beam, studied by The core on which the molecular beam, the ionization detector, and the selective amplifier fall is so strong that, in order to simplify the measurements, the test surface is placed inside the deceleration chamber of the molecular beam combined with the ionization detector and representing a closed volume with a hole. Sources of information taken into account in the examination of -i.TH.Heaea 3H.perfpntncince about: ... l L./h A and L LA L L I tL. H .21 KAass Spe6t, rpmet r40 K 6c & uUa-tea cv t Betectonfor Scis-Sufrcfcft nteoict-lon NAeasurements ,, Vacuum; 17, No. 9, 1967.

2.Y.R. Bfogi, D JsA.Tpavep anS MR8usVv „Condenecftiott of 30o-2500Kcfc (ses en surfaces at chVocfeniotewp & Vi / tu-“ „3he Science of Science prototype).