Ulvac CRYO-U Series Instruction Manual page 16

Installation
Although the maximum allowable working temperature of the refrigerator unit is
70°C, the temperature of the internal components such as 80K shield, 80K baffles,
15K cryopanel or refrigerator unit must be kept lower than 20°C during bake-out.
It is required to mount a temperature controller for overheat protection.
Mount a K thermocouple (supplied by customers) to the thermocouple mounting screw
on outer surface of the cryopump body (refer to Figure 1-2 of "1. SPECIFICATIONS").
Also adjust the surface temperature of the pump body to prevent the 80K shield from
being heated above 20°C by taking the output signal of the K thermocouple mounted on
the 80K shield (refer to Figure 1-2 of "1. SPECIFICATIONS") into the temperature
controller for overheat protection.
The set temperature of the surface of the pump body is approximately 250°C. However,
the temperature of the components during the warm-up process varies widely
depending on the cryopump models and heat insulation methods of the pump body.
When baking the pump body for the first time, the temperature setting should be made
lower to examine and determine the appropriate temperature setting so that the 80K
shield does not exceed 20
severe damage to the refrigerator unit and the thermocouple.
When using an O-ring for a vacuum seal of the inlet flange and the accessory port, set
the temperature for bake-out with attention to the heatproof temperature.
Figure 2-1 shows an example of the control circuit for baking.
AC200V
CT2
T2
Figure 2-1
2-2
°C
(does not overshoot). Ignoring this process may result in
SW1
H
SSR
Signal line for set temperature control
CT1
Example of Control Circuit for Baking
ULVAC CRYOGENICS INCORPORATED
CAUTION
：Sheath Heater
H
ＳＷ１：ON/OFF switch for baking
ＣＴ１：Temperature controller for baking
ＣＴ２：Temperature controller for
overheat protection
Ｔ１ ：Surface temperature of cryopump
Ｔ２ ：Temperature of 80K shield
SSR ：Solid state relay
T1