11 shown only in fig1 is disposed upstream of a pump inlet opening 9 which is equipped with a baffle 7 valve 11 includes the fixed disc 12 and a rotatable disc 13 each provided with essentially radial slotted openings the valve is actuated by rotation of disc 13 in the embodiment according to fig1 housing 2 of cryopump 1 is provided approximately at the level of stage 4 of the first refrigerator stage with a pipe connection 14 which supports a monitoring device marked 15 this device comprises a circuit for supplying heating devices 16 and 17 with which cooling heads 4 and 5 of the two stage cooling head 3 are equipped a vacuum tight passage 23 is provided for connecting lines 18 and 19 between supply device 15 and heating devices 16 17 in the region of flanges 21 22 at supply device 15 and at pipe connection 14 respectively additionally the cryopump includes a temperature sensor 24 which is provided at cooling stage 4 and whose measuring line 26 also leads to monitoring device 15 a supply unit 27 shown as a block is connected with this monitoring device 15 in addition to its function as an excess temperature protection during regeneration by means of electrical heaters the monitoring device 15 serves to ensure the setting of the desired temperature of cooling stage 4 and of the pump surfaces and shieldings 6 7 supported thereby for this purpose the temperature of cooling stage 4 is measured with the aid of sensor 24.