Cryopump and method of operating same

A cryopump and a method of operating the same, with the cryopump being provided with a cryopanel adapted to be cooled with cold heat generated by a cold heat generating device, and remove the ambient gas, and a device for regulating the temperature of said cryopanel in accordance with the ambient conditions. The cryopump is capable of varying its pumping speed by regulating in accordance with the ambient conditions the temperature of the cryopanel which is adapted to be cooled with cold heat and remove the ambient gas.

BACKGROUND OF THE INVENTION 
This invention relates to a cryopump and a method of operating the same, 
and more particularly, to a method and cryopump carring out a pumping 
operation while varying a pumping speed. 
In, for example, U.S. Pat. No. 4,285,710, a cryopump of the aforementioned 
type is proposed wherein a two-stage expander comprises a first-stage 
expansion chamber and a second-stage expansion chamber. An aluminum 
support structure is attached to a distal end wall of the first-stage 
expansion chamber. A cylindrical pumping structure, constituting a 
first-stage pumping structure, is attached to the aluminum support 
structure so that the former is in an intimate thermal contact with the 
latter. A plate is attached to an end wall of the second-stage expansion 
chamber, and a frustoconical member, constituting a second-stage pumping 
structure, is attached to the plate so that the frustoconical member 
skirts a portion of the second-stage expansion chamber. A variable 
aperture flow restricting device is attached directly to a first (i.e. 
warmer) stage of a two-stage cryogenic pumping structure. Such a pumping 
apparatus is placed in a housing structure. 
In this cryopump, the first-stage expansion of a helium gas occurs in the 
first-stage expansion chamber, so that the first-stage temperature is 
selected typically in the range of 50.degree.-80.degree. K. The 
second-stage expansion of the helium gas occurs in the second-stage 
expansion chamber, so that the second-stage temperature is selected 
typically in the range of 10.degree.-20.degree. K. The temperatures 
attainable in the first and second refrigeration stages are determined by 
the parameters of a refrigeration system. On the other hand, the 
temperature of the variable aperture flow restricting device, which 
requires a constant pumping speed, is maintained at such a cryogeneric 
temperature that is lower than the condensation temperature of gases (e.g. 
water vapor, carbon dioxide) and not lower than the condensation 
temperature of a selected gas (e.g. argon). The controlled variation at a 
pumping speed of this selected gas may be provided by throttling the 
apertured portion of the variable aperture flow restricting device. 
The above proposed cryopump is used suitably in a sputtering system, and is 
capable of removing a gas, such as argon from a sputtering chamber as a 
constant water vapor pumping speed is maintained, at a different speed. 
However, disadvantages of the above described cryopump resides in the fact 
that a cross-sectional area of a space through which a gas passes and the 
conductance decrease due to the variable aperture flow restricting device. 
Accordingly, a maximum pumping speed of the proposed cryopump decreases as 
compared with a cryopump which uses an expansion means having the same 
cold heat generating capacity, and no pumping speed varying functions. For 
example, if the variable aperture flow restricting device mentioned above 
is provided in a cryopump having no pumping speed varying functions, for 
example, a cryopump having a maximum pumping speed of 3000 l/s, the 
maximum pumping speed decreases to substantially 1500 l/s even when the 
throttling is done so as to obtain a maximum degree of opening of the 
variable aperture of this device. Namely, providing the variable aperture 
flow restricting device in a cryopump to furnish the pump with the pumping 
speed varying functions means reduces the maximum pumping speed thereof. 
An object of the present invention is to provide a cryopump capable of 
varying a pumping speed by regulating, in accordance with ambient 
conditions, a temperature of a cold panel, and a method of operating the 
same. 
The present invention enables a pumping speed of a cryopump, provided with 
a cryopanel cooled with the cold heat from a cold heat generating means to 
remove an ambient gas, and a means for regulating, in accordance with 
ambient temperature, the temperature of the cryopanel, to be varied by 
operating the cryopump while regulating the temperature of the cryopanel.

DETAILED DESCRIPTION 
An embodiment of the present invention will now be described with reference 
to FIG. 1. 
Referring now to the drawings wherein like reference numerals are used 
throughout the various views to designate like parts and, more 
particularly, to FIG. 1, a cryopump is provided with first- and 
second-stage cryopanels 30, 31 which are attached to a first and second 
cold stations in first- and second-stage expansion means or refrigerating 
members 21, 22 in, for example, a two-stage regenerating refrigerator 
generally designated by the reference numeral 20 in a cold heat generating 
means. The cold heat generating means includes, for example, a compressor 
10 adapted for a working gas of room temperature and a low pressure, to 
compress the same and discharge a working gas of room temperature and a 
high pressure therefrom, and an expansion means adapted to adiabatically 
expand the working gas of room temperature and a high pressure discharged 
from the compressor 10, to generate cold heat and, for example, the 
refrigerator 20. The refrigerator 20 is cooled with the cold heat 
generated by the first- and second-stage refrigerating members 21, 22, to 
condense or solidify the ambient gas and thereby remove the same. Means 
are provided for regulating the temperature of a cryopanel, in this case, 
the second-stage cryopanel 31. The first- and second-stage refrigerating 
members 21, 22 in the refrigerator 20 and the first- and second-stage 
cryopanels 30, 31 are housed in a vessel 40. The portion of the vessel 40, 
opposed to the second-stage cryopanel 31, is opened. A baffle 50 is joined 
to the first-stage cryopanel 30 so that the baffle 50 is positioned 
between the second-stage cryopanel 31 and the opening of the vessel 40. 
When the vessel 40 is joined to a part into which the gas is pumped, for 
example, a vacuum chamber 60 so that the former is communicated with the 
latter via the opening of the former, the cryopump is rendered capable of 
evacuating the vacuum chamber 60. The means for regulating the temperature 
of the second-stage cryopanel 31 includes a pressure sensor 70 working as 
a means for detecting the ambient pressure, and a means for controlling a 
flow rate of the working gas which is supplied to the refrigerator 20, in 
accordance with a signal which the control means receives from the 
pressure sensor 70. This control means includes a means for converting the 
revolution number of a driving motor for the compressor 10, for example, 
an inverter 71, and a control unit 72a adapted to receive a signal from 
the pressure sensor 70 and control an output frequency from the inverter 
71 in accordance with a difference between a preset pressure and a 
pressure detected by the pressure sensor 70. The pressure sensor 70 in 
FIG. 1 is provided so that it can detect the pressure in the vacuum 
chamber 60. The inverter 71 is provided outside the vessel 40 and is 
vacuum chamber 60 and connected to the driving motor for the compressor 10 
through a lead wire 73a. The control unit 72a is provided outside vessel 
40 and vacuum chamber 60, and the pressure sensor 70 and inverter 71 are 
connected to this control unit 72a through lead wires 73b, 73c, 
respectively. The baffle 50 in use is identical with the baffle used in a 
conventional cryopump having no pumping speed varying functions. Since the 
regulation of the pumping speed at the baffle 50 in FIG. 1 is not 
required, it is formed to such a shape that enables a maximum 
cross-sectional area of the part (aperture portion) through which a gas 
passed to be obtained, i.e., the pumping speed of the gas which can be 
removed by the second-stage cryopanel 31 to become the highest. 
Referring to FIG. 1, the operations of the compressor 10 and refrigerator 
20 are started at room temperature. At this time, the roughing operation 
in the vacuum chamber 60 shall have been completed. Simultaneously with 
the starting of the operations of the compressor 10 and refrigerator 20, 
the temperature in the second cold station in the second-stage 
refrigerator 22 begins to go down, and this temperature reaches a 
substantially constant level in 1-2 hours, though the length of this time 
varies with the size of the cryopump. In accordance with such a 
temperature drop at the second cold station in the second-stage 
refrigerator 22, the temperature of the second-stage cryopanel 31 goes 
down, so that the pressure in the vacuum chamber 60 drops. The variations 
in the pressure in the vacuum chamber 60 is detected by the pressure 
sensor 70, and a signal representative of the results of this detection is 
inputted into the control unit 72a. When the pressure, which has been 
detected by the pressure sensor 70, in the vacuum chamber 60 becomes lower 
during this time than the pressure set in advance in the control unit 72a, 
the output frequency of the inverter 71 is reduced by the control unit 
72a. Consequently, the revolution number of the compressor 10 decreases, 
and the flow rate of the working gas of room temperature and a high 
pressure discharged from the compressor 10 and supplied to the 
refrigerator 20 decreases. Due to such a decrease in the flow rate of the 
working gas, the amount of generation of cold heat in the second-stage 
refrigerator 22 decreases, and the temperature of the second cold station 
in the same refrigerator 22 rises in accordance with the degree of 
decrease in this generation rate. In accordance with the rise in the 
temperature of the second cold station in the second-stage refrigerator 
22, the temperature of the second-stage cryopanel 31 rises, so that the 
pressure in the vacuum chamber 60 rises. On the other hand, when the 
pressure, which has been detected by the pressure sensor 70, in the vacuum 
chamber 60 becomes higher than the pressure (which may be equal to or 
different from the above-mentioned set pressure) set in advance in the 
control unit 72a, the output frequency of the inverter 71 is increased by 
the control unit 72a. As a result, the revolution number of the compressor 
10 increases, and the flow rate of the working gas of room temperature and 
a high pressure discharged from the compressor 10 and supplied to the 
refrigerator 20 increases. Due to such an increase in the flow rate of the 
working gas, the amount of generation of cold heat in the second-stage 
refrigerator 22 increases, so that the temperature of the second cold 
station in the same refrigerator 22 goes down in accordance with the 
degree of increase in the mentioned generation rate. In accordance with 
such a temperature drop at the second cold station in the second-stage 
refrigerator 22, the temperature of the second-stage cryopanel goes down, 
so that the pressure in the vacuum chamber 60 drops. With the embodiment 
of FIG. 1, the pumping speed of the cryopump can be varied without 
sacrificing the maximum pumping speed of the gas which can be removed by 
the second-stage cryopanel 31, by regulating the temperature of this 
cryopanel. Moreover, since the discharge rate of the working gas from the 
compressor can be controlled in accordance with the pressure in the vacuum 
chamber 60, the wasteful use of the power for operating the compressor can 
be prevented, so that the cost of operating the cryopump can be saved. 
Additionally, a conventional cryopump without its own pumping speed 
varying functions can be modified to a pumping speed-variable cryopump by 
merely providing a pressure sensor 70, an inverter 71 and a control unit 
72a in the former cryopump in the above-mentioned manner. 
When the cryopump of FIG. 1 is applied to an apparatus, in which it is 
necessary to vacuum the interior of a vacuum chamber 60 from the 
atmospheric pressure to a predetermined pressure, and then carry out an 
operation while retaining the pressure in a predetermined level in, for 
example, an argon gas atmosphere, the consumption of the argon gas can be 
minimized. In order to maintain the pressure in the vacuum chamber 60 in a 
predetermined level, it is necessary that the argon gas be supplied from 
the outside into the vacuum chamber 60 at such a flow rate that correspond 
to that of the argon gas removed therefrom. In this embodiment, the 
pumping speed in the cryopump is set in a low level to reduce the flow 
rate of the argon gas removed from the vacuum chamber 60. Accordingly, the 
flow rate of the argon gas supplied from the outside into the vacuum 
chamber 60 can be correspondingly reduced so that the consumption of argon 
gas can be minimized. 
Referring to FIG. 2, a means for controlling a flow rate of a working gas, 
which is supplied to a refrigerator 20, upon receipt of a signal from a 
pressure sensor 70 includes a bypass pipe 74a, a variable flow rate valve 
75a and a control unit 72b adapted to receive a signal from the pressure 
sensor 70 and control the degree of opening of the variable flow rate 
valve 75a in accordance with a difference between a preset pressure and 
the pressure detected by the pressure sensor 70. 
As shown in FIG. 2, a discharge port for the working gas of the compressor 
10 and a feed port of the refrigerator 20 are connected together by a 
high-pressure pipe 74b. A discharge port for the working gas of the 
refrigerator 20 and a suction port of the compressor 10 are connected 
together by a low-pressure pipe 74c. A bypass pipe 74a is connected to its 
one end to the high-pressure pipe 74b, and at the other end thereof to the 
low-pressure pipe 74c. The flow rate-variable valve 75a is provided in the 
bypass pipe 74a. The control unit 72b is provided outside the vessel 40 
and vacuum chamber 60, and the pressure sensor 70 and the flow 
rate-variable valve 75a are connected to the control unit 72b through lead 
wires 73b, 73d, respectively. 
For example, when the pressure in the vacuum chamber 60 in the embodiment 
of FIG. 2, which has been detected by the pressure sensor 70, becomes 
lower than the pressure set in advance in the control unit 72b, the degree 
of opening of the flow rate-variable valve 75a is increased by the same 
control unit 72b. Consequently, a part of the working gas of room 
temperature and a high pressure, which is discharged from the compressor 
10 and flows through the high-pressure pipe 74b, is introduced into the 
bypass pipe 74a. This causes the flow rate of the working gas of room 
temperature and a high pressure supplied to the refrigerator 20 to 
decrease. As a result, a phenomenon similar to the phenomenon described 
above in connection with the embodiment of FIG. 1 occurs, so that the 
pressure in a vacuum chamber 60 increases. When the pressure, which has 
been detected by the pressure sensor 70, in the vacuum chamber 60 becomes 
higher than a pressure (which may be equal to or different from the 
above-mentioned set pressure) set in advance in the control unit 72b, the 
degree of opening of the flow rate-variable valve 75a is lowered by the 
control unit 72b. Consequently, the flow rate of the part of the working 
gas of room temperature and high pressure discharged from the compressor 
10 and flows through the high-pressure pipe 74b which is introduced into 
the bypass pipe 74a decreases to a low level or zero, so that the flow 
rate of the working gas of room temperature and high pressure supplied to 
the refrigerator 20 increases. As a result, a phenomenon similar to the 
phenomenon referred to in the description of the embodiment of FIG. 1 
occurs to cause the pressure in the vacuum chamber 60 to drop. 
With the embodiment of FIG. 2, the pumping speed of the cryopump can be 
varied without sacrificing the maximum pumping speed of the gas which can 
be removed by the second-stage cryopanel 31, by regulating the temperature 
of the same cryopanel. 
Moreover, a conventional cryopump without its own pumping speed varying 
functions can be modified to a pumping speed-variable cryopump by merely 
providing a pressure sensor 70, a bypass pipe 74a, a flow rate-variable 
valve 75a and a control unit 72b in the former cryopump in the 
above-mentioned manner. 
Additionally, since the inverter 71 in the embodiment of FIG. 1 can be 
omitted, the modifying of a cryopump having no pumping speed varying 
functions to a pumping speed-variable cryopump can be done at a low cost. 
Referring to FIG. 3, a means for controlling a flow rate of a working gas, 
which is supplied to a refrigerator 20, in accordance with a signal from a 
pressure sensor 70 is constituted by a valve 75b, and a control unit 72c 
adapted to receive a signal from the pressure sensor 70 and control the 
degree of opening of the valve 75b in accordance with a difference between 
the pressure set in advance and the pressure detected by the pressure 
sensor 70. 
Referring to FIG. 3, the valve 75b is provided in a high-pressure pipe 74b. 
The control unit 72c is provided outside a vessel 40 and a vacuum chamber 
60, and the pressure sensor 70 and valve 75b are connected to the control 
unit 72c through lead wires 73b, 73e, respectively. 
For example, the pressure, which is detected by the pressure sensor 70, in 
the vacuum chamber 60 in the embodiment of FIG. 3 becomes lower than the 
pressure set in advance in the control unit 72c, the degree of opening of 
the valve 75b is reduced by the control unit 72c. Accordingly, the flow 
rate of the working gas of room temperature and high pressure supplied to 
the refrigerator 20 decreases. Consequently, a phenomenon similar to the 
phenomenon referred to in the description of the embodiment of FIG. 1 
occurs, so that the pressure in the vacuum chamber 60 rises. When the 
pressure, which is detected by the pressue sensor 70, in the vacuum 
chamber 60 becomes higher than the pressure (which may be equal to or 
different from the above-mentioned set pressure) set in advance in the 
control unit 72c, the degree of opening of the valve 75b increased by the 
control unit 72c. This causes the flow rate of the working gas of room 
temperature and high pressure supplied to the refrigerator 20 to increase. 
As a result, a phenomenon similar to the phenomenon referred to in the 
description of the embodiment of FIG. 1 occurs, so that the pressure in 
the vacuum chamber 60 drops. 
With the embodiment of FIG. 3, the pumping speed of the cryopump can be 
varied without sacrificing the maximum pumping speed of the gas wich can 
be removed by the second-stage cryopanel 31, by regulating the temerature 
of the same cryopanel. 
Additionally, a conventional cryopump without its own pumping speed varying 
functions can be modified to a pumping speed-variable cryopump by merely 
providing a pressure sensor 70, a valve 75 and a control unit 72a in the 
former cryopump in the above-mentioned manner. 
Moreover, since the bypass pipe 74a used in the embodiment of FIG. 2 can be 
omitted, the modifying of a cryopump having no pumping speed-varying 
functions to a pumping speed-variable cryopump can be done at a further 
low cost. 
The embodiment of FIG. 4 differs from the embodiment of FIG. 1 in that a 
means for regulating the temperature of a second-stage cryopanel 31 a 
temperature sensor 76 constituting a means for detecting the temperature 
of the second-stage cryopanel 31, and a means adapted to receive a signal 
from the temperature sensor 76 and control the flow rate of a working gas 
supplied to a refrigerator 20, with the means for controlling the flow 
rate of the working gas including a means for converting the revolution 
number of a driving motor for a compressor 10, for example, an inverter 
71, and a control unit 72d adapted to receive a signal from the 
temperature sensor 76 and control the output frequency of the inverter 71. 
Referring to FIG. 4, the temperature sensor 76 is provided on the 
second-stage cryopanel 31, and the temperature sensor 76 and inverter 71 
are connected to the control unit 72d through lead wires 73f, 73g, 
respectively. 
Referring to FIG. 4, in order to vary the pumping speed which corresponds 
to the temperature of the second-stage cryopanel 31 detected by the 
temperature sensor 76, the output frequency of the inverter 71 may be 
varied by the control unit 72d. Due to the variation in the output 
frequency of the inverter 71, the flow rate of the working gas of room 
temperature and high pressure discharged from the compressor 10 and 
supplied to the refrigerator 20 increases or decreases, so that the amount 
of generation of cold heat in the second-stage refrigerator 22 increases 
or decreases. Such an increase or decrease in the amount of generation of 
cold heat causes the temperature of the second-stage cryopanel 31 to drop 
or rise, and the pumping speed varies in accordance with this result. 
In the embodiment of FIG. 4, the same effect as in the the embodiment of 
FIG. 1 can be obtained. 
In the embodiment of FIG. 4 as well, the temperature of the second cold 
station in the second-stage refrigerator 22 reaches a substantially 
constant level in 1-2 hours due to the starting of the operations of the 
compressor 10 and refrigerator 20 as referred to in the description of the 
embodiment of FIG. 1. The flow rate Q of the working gas required by the 
refrigerator 20 increases as shown by a broken line in FIG. 5, immediately 
after the starting of the operation thereof and in accordance with a drop 
in the temperature T of the second cold station in the second-stage 
refrigerator 22, the flow rate Q becoming constant at the same time that 
the temperature T becomes constant. About 2-3 times of increase in the 
flow rate of the working gas is required by the refrigerator 20 during the 
period of time between an instant which is immediately after the starting 
of the operation and an instant at which the constant operational 
condition is obtained. This indicates that, if a base flow rate of the 
working gas of 100% is set as the flow rate thereof required by the 
refrigerator 20 in a constant operational condition, the flow rate of the 
working gas at the time which is immediately after the starting of the 
operation may be about 30-50%. Since this rate of increase is determined 
by the size of the refrigerator, the relation between the temperature 
level of the second-stage refrigerator 22 and a required flow rate of a 
working gas therefor in the same type of cryopumps can be determined by 
making an experiment on a selected cryopump in advance. Accordingly, when 
the determined relation between the temperature level of the second-stage 
refrigerator 22 and a required flow rate of the working gas therefor is 
inputted into the control unit 72d to control the output frequency of the 
inverter 71 on the basis of this relation and the temperature, which is 
detected by the temperature sensor 76, of the second-stage cryopanel 31, 
the wasteful use of the power for operating the compressor during the 
period of time between the instant at which the operation is started and 
the instant at which the constant operational condition is obtained can be 
prevented, and the cyopump-operating cost can be minimized. 
The embodiment of FIG. 6 differs from the embodiment of FIG. 4 in that a 
means for controlling the flow rate of a working gas consists of a bypass 
pipe 74a, a flow rate-variable valve 75a and a control unit 72e adapted to 
receive a signal from a temperature sensor 76 nad control the degree of 
opening of the flow rate-variable valve 75a. 
In the embodiment of FIG. 6, the bypass pipe 74a is connected at its one 
end to a high-pressure pipe 74b, and at the other end thereof to a 
low-pressure pipe 74c. The flow rate-variable valve 75a is provided in the 
bypass pipe 74a. The control unit 72e is provided outside a vessel 40 and 
a vacuum chamber 60, and the temperature sensor 76 and flow rate-variable 
valve 75a is connected to the control unit 72e through lead wires 73f, 
73h, respectively. 
Referring to FIG. 6, in order to vary the pumping speed coresponding to the 
temperature detected by the temperature sensor 76 of a second-stage 
cryopanel 31, the degree of opening of the flow rate-variable valve 75a 
may be caried by the control unit 72e. Due to the variation of the degree 
of opening of the flow rate-variable valve 75a, the flow rate of the 
working gas of room temperature and high pressure supplied to a 
refrigerator 20 increases or decreases, so that the amount of generation 
of cold heat in a second-stage refrigerator 22 increases or decreases. In 
accordance with such an increase or a decrease in the amount of generation 
of cold heat, the temperature of the second-stage cryopanel 31 drops or 
rises, so that the pumping speed varies correspondingly. 
In the embodiment of FIG. 6, the same effects as in the embodiment of FIG. 
2 can be obtained. 
The embodiment of FIG. 7 differs from the embodiment of FIG. 4 in that a 
means for controlling the flow rate of a working gas including a valve 
75b, and a control unit 72f adapted to receive a signal from a temperature 
sensor 76 and control the degree of opening of the valve 75b. 
In the embodiment of FIG. 7, the valve 75b is provided in a high-pressure 
pipe 74b. The control unit 72f is provided outside a vessel 40 and a 
vacuum chamber 60, and the temperature sensor 76 and valve 75b are 
connected to the control unit 72f through lead wires 73f, 73i, 
respectively. 
Referring to FIG. 7, in order to vary the pumping speed corresponding to 
the temperature of a second-stage cryopanel 31, which is detected by the 
temperature sensor 76, the degree of opening of the valve 75b may be 
varied by the control unit 72f. Due to the variation in the degree of 
opening of the valve 75b, the flow rate of a working gas of room 
temperature and high pressure supplied to the refrigerator 20 increases or 
decreases, so that the amount of generation of cold heat in the 
second-stage refrigerator 22 increases or decreases. Due to such an 
increase or a decrease in the amount of generation of cold heat, the 
temperature of the second-stage cryopanel 31 drops or rises, and the 
pumping speed varies in accordance with this result. 
In the embodiment of FIG. 7, the same effects as in the embodiment of FIG. 
3 can be obtained. 
The embodiment of FIG. 8 differs from the embodiment of FIG. 1 in that a 
means for regulating the temperature of a second-stage cryopanel 31 
includes an electric heater 77, a power source 78 and a switch 79. 
Referring to FIG. 8, the electric heater 77 is wound around a second cold 
station in a second-stage refrigerator 22. The power source 78 is provided 
outside a vessel 40 and a vacuum chamber 60, and the electric heater 77 is 
connected to the power source 78 through a lead wire 73j and a lead wire 
73k on which the switch 79 is provided. 
In order to, for example, reduce the actual pumping speed of the embodiment 
of FIG. 8, the power source 78 and switch 79 may be turned on to apply an 
electric current to the electric heater 77. When the electric heater 77 is 
thus turned on, the heat is generated therein, so that the temperature of 
the second-stage cryopanel 31 rises through a second cold station in the 
second-stage refrigerator 22. Due to such a temperature rise, the pumping 
speed decreases to a low level owing to the second-stage cryopanel 31. In 
order to increase the pumping speed, which is thus reduced to a low level, 
to a high level, the supply of an electric current from the power source 
78 to the electric heater 77 may be cut off, or the flow rate of this 
electric current may be reduced. With the embodiment of FIG. 8, the 
pumping speed of the cryopump can be varied without sacrificing the 
maximum pumping speed of the gas which can be collected by the second-type 
cryopanel 31, by regulating the temperature of the same cryopanel. 
Furthermore, a conventional cryopump without its own pumping speed varying 
functions can be modified to a pumping speed-variable cryopump by merely 
providing an electric heater 77, a power source 78 and a switch 79 in the 
former cryopump in the above-mentioned manner. Additionally, the electric 
heater 77 is used during an operation for regenerating the second-stage 
cryopanel 31, the warm up time to room temperature in the cryopanel 31 can 
be reduced, so that the time required to carry out the cryopanel 
regenerating operation can be reduced. 
If a device capable of automatically controlling the voltage of the power 
source 78 in accordance with the temperature of the second-stage cryopanel 
31, the pumping speed can be varied arbitrarily by merely setting the 
temperature of this cryopanel 31 by the mentioned device. 
The embodiment of FIGS. 9 and 10 differs from the embodiment of FIG. 8 in 
that a heater mounting member 80 is provided on the portion of a 
second-stage cryopanel 31 which is around a second cold station in a 
second-stage refrigerator 22 with an electric heater 77 wound around the 
heater mounting member 80. 
In the embodiment of FIGS. 9 and 10, the same effects as in the embodiment 
of FIG. 8 can be obtained as well as the following additional effects. 
With the embodiment of FIGS. 9 and 10, the temperature of the cryopanel 
attached to the refrigerator can be increased effectively without 
accompanying a great increase in the temperature of the second cold 
station in the second-stage refrigerator 22. This enables the cryopanel 
regenerating time to be further reduced. 
Moreover, when it becomes necessary, during a cryopump repairing operation, 
to take the first-stage refrigerator, first-stage cryopanel, second-stage 
refrigerator and second-stage cryopanel out of the vessel, the lead wire 
of the electric heater 77 may not be cut off each time. Accordingly, the 
time required for the repair work can be reduced. 
The embodiment of FIG. 11 differs from the embodiment of FIG. 8 in that a 
means for regulating the temperature of a second-stage cryopanel 31 
includes a heating pipe 81, and a heating fluid supply source. 
In the embodiment of FIG. 11, the heating pipe 81, is for example, wound 
spirally around a second cold station in the heating pipe 81. The heating 
fluid supply source includes, for example, a compressor 10, a heating 
fluid supply pipe 82a, a heating fluid return pipe 82b and a valve 83. One 
end of the heating fluid supply pipe 82a is connected to an inlet for a 
heating fluid of the heating pipe 81, and one end of the heating fluid 
return pipe 82b to an outlet for a heating fluid of the heating pipe 81. 
The other end of the heating fluid supply pipe 82a joins a high-pressure 
pipe 74b, and the other end of the heating fluid return pipe 82b a 
low-pressure pipe 74c. The valve 83 is provided in the portion of the 
heating fluid supply pipe 82a which is outside a vessel 40 and a vacuum 
chamber 60. 
Referring to FIG. 11, in order to, for example, reduce the actual pumping 
speed, the valve 83 may be opened to supply a working gas of room 
temperature and high pressure to the heating pipe 81. Due to the working 
gas of room temperature, the temperature of a second-stage cryopanel 31 
increases via a second cold station. Due to such a temperature rise, the 
pumping speed at the second-stage cryopanel 31 becomes low. In order to 
increase the pumping speed which has thus been reduced, the supplying of 
the working gas of room temperature and high pressure to the heating pipe 
81 may be stopped, or the flow rate thereof may be reduced. The pressure 
of the working gas of room temperature and high pressure is reduced while 
it passes through the heating pipe 81. After this working gas has then 
passed through the heating fluid return pipe 82b, it joins a working gas 
of low pressure passing through the low-pressure pipe 74c to be then 
returned to the compressor 10. If a device, which is not shown in FIG. 11, 
for automatically opening and closing the valve 83 in accordance with the 
temperatures of the second cold station and second-stage cryopanel 31 is 
used, the pumping speed can be varied arbitrarily by merely setting the 
temperatures at the second cold station and second-stage cryopanel 31 by 
the device. 
In the embodiment of FIG. 11, the same effects as in the embodiment of FIG. 
7 can be obtained, as well as the following effects. 
With the embodiment of FIG. 11, since an electric heater and a power source 
are not required, the cost of operating the cryopump can further be 
reduced, and the construction thereof can be simplified. 
The embodiment of FIG. 12 differs from the embodiment of FIG. 11 in that a 
heating pipe-mounting member 84 is provided on the portion of the 
second-stage cryopanel 31 which is around the second cold station with a 
heating pipe 81 wound spirally around this mounting member 84. 
In the embodiment of FIG. 12, the same effects as in the embodiment of FIG. 
11 can be obtained, as well as the same effects as in the embodiment of 
FIGS. 9 and 10. 
The pressure sensor, which is provided in the vacuum chamber 60 in the 
embodiments of FIGS. 1, 2 and 3, may be provided in the vessel so that the 
pressure therein can be detected. In the embodiments of FIGS. 1 and 4, an 
inverter 71 is used as a means for converting the revolution number of the 
driving motor for the compressor; a means using gears may also be used for 
the same purpose. In the embodiments of FIGS. 11 and 12, a working gas of 
room temperature and high pressure is supplied to the heating pipe. If 
this working gas is a gas (or a fluid) having a solidifying point of not 
more than 40K, it can be used without being solidified in the heating 
pipe. 
The present invention described above can provide a method of operating a 
cryopump and a cryopump which is provided with a cryopanel cooled with 
cold heat generated by a cold heat generating means, to remove the ambient 
gas, and a means for regulating the temperature of the cryopanel, and 
which is capable of varying the pumping seed by operating the cryopump 
while regulating, in accordance with ambient conditions, the temperature 
of the cryopanel.