Typical Pressure Variations During; Troubleshooting The Cryopump - HELIX CTI-CRYOGENICS CRYO-TORR 100 Installation, Operation And Servicing Instructions

5.4 Startup and Cooldown
I. Before startup confmn the following:
a. That the Hi-Vac valve to your vacuum chamber
is closed.
b. That the pressure in your cryopump is approxi-
mately 100 microns.
2. Turn on the system power ON/OFF switch on the
controller/compressor.
3. Note the helium pressure and temperature reading
during the initial cooldown. Typical values during
cooldown are given in Table 5.1. If the cryopump
ai-CRYOGENICS
-------- --
-
-------
1j_~~_I_)(_,_!_~_c::H_!::JQY2~~
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<:(J~~9_~~~19N
has not achieved a second stage tempemture of
20K or less in the time specified in Table 5.1 with
the Hi-Vac valve closed, refer to the Appendix A,
Troubleshooting the Cryopump.
4. When the cooldown temperature of20K or less is
reached, the cryopump is ready for normal vacuum
operation. An additional 30 minutes will often permit
the cryopump to reach "bottom-out" temperature.
5. Record the time that was required
to
reach 20K
in your log; also record the compressor return gas
pressure at 20K. This value can be useful for future
evaluation of cryopump performance.
Table 5.1 Typical Pressure Variations During Cooldown and Normal Operation
(All Values Nominal)
COMPRESSOR
CRYOPUMP MODEL NOMINAL TEMPERATURE
H:Vp
MODEL (CONTROLLER) HELIUM INDICATOR READING
(QTY. USED) MODEL TIME PRESSURE PSIG (kPa)* READING(k)
(psla)
CT-7 8300
Before startup 250 (1725)
300
---
or
(8001,8002) 60 mins. after startup 95 (655) W
"<
20
CT-l00
(1)
CT-8 8300 Before startup
250 (1725) 300
..
-
(I)
(8001,8002) 90 mins. after startup 105 (725) 20
"<
20
or
CT-8F
(1)
CT-l00 8300
Before startup
250 (1725) 300
..
-
(2)
(8002) 60 mins. after startup
95 (655)
20
"<
20
CT-l00
SC Before startup
225 (1550) 300
--
(I) 120 mins .• rter startup 250 (1725) IO-W
"<
20
CT·7
SC Before startup
225 (1550) 300
...
(1)
90 mins. after startup
250 (1725)
IO·W
"<
20
CT·8
SC
Before startup
247 (1707) 300
...
or 90
mins •• rter startup
280(1930)
IO-W
"<
20
CT·8F
·Center point of needle swing
6. 7
i ;
•
5-2