Browse Prior Art Database

Cryopump System

IP.com Disclosure Number: IPCOM000121465D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 83K

Publishing Venue

IBM

Related People

Rabe, G: AUTHOR

Abstract

This article refers to a cryopump system which is temperature-feedback-controlled by a frequency-controlled cold head motor. The displacement frequency of the coolant (in this case, helium) permits operating the pump within a narrow temperature range.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Cryopump System

      This article refers to a cryopump system which is
temperature-feedback-controlled by a frequency-controlled cold head
motor.  The displacement frequency of the coolant (in this case,
helium) permits operating the pump within a narrow temperature range.

      The cryopump is used to produce a high vacuum which is
absolutely free from hydrocarbon, starting at a pressure of 100 Pa
and ending in a 10-3 Pa range.  The process pressure can be kept to
several Pa corresponding to the gas flows. The interior of the
cryopump is made up of two cold surfaces, called first and second
stage arrays.  These arrays are cooled down to their specific
temperature of 77oK and 13oK, respectively.

      The first array, a sheet-metal cylinder with a front baffle, is
cooled to a temperature ranging from 50oK to 80oK.  The baffle is
designed to pump a maximum amount of water vapor.  The second array,
a metal plate with bonded charcoal, is designed to capture a wide
variety of gases by retaining them as ice crystals or absorbing them
into the capillary holes of the charcoal.  This second stage array is
typically cooled to 10oK to 15oK.

      The final temperatures of the arrays are subject to the heat
load created by the gas flow and the radiation to the pump and
chamber walls.  Depending upon the ice layers and the compressor and
cold head condition, the first and second arrays reach a final
temperature of 80oK - 50oK and 15oK - 10oK, respectively.  Only the
second stage array is provided with a temperature sensor (silicon
diode).  An additional temperature measurement on the first stage
array is recommendable.

      F...