Supply and Installation of a 1.8 to 300 K Cryostat to the University of Birmingham

Descriptions

The University of Birmingham invites tenders for supply of a variable temperature cryostat system, for carrying out experiments in condensed matter physics. The system is to be provided with the pumps, compressors, filters, and reservoirs necessary for its operation. A magnetic power supply is to be provided. Three measurement inserts are to , be provided: a standard (that is, sample-in-exchange-gas) insert, a sample-in-vacuum , insert, and a 3-helium insert. , Specification, i. Magnet, 1) A field range of +12 T, for sample temperatures over the entire specified range., 2) A minimum field homogeneity of +0.1% over a 1 cm diameter about the field centre., 3) Ramping from 0 T to +12 T or -12 T should take an hour or less., 4) The time to cool the magnet from 300 K to its operating temperature should be specified., 5) The magnet should include a persistence mode., 6) Information should be provided on the type of magnet wire that will be used, and, if available, expected hysteresis., ii. Magnet power supply, 7) The current resolution and stability of the magnet power supply should be specified., iii. Variable temperature insert (VTI), 8) The temperature range must be at least 1.8 to 300 K., 9) The temperature sensor type, the source of its calibration, and its location should be specified., 10) The cool-down time from 300 K to 1.8 K should be specified, under an assumption that the magnet is already at its operating temperature., 11) The termination at the top of the variable temperature insert should be specified; a KF 50 flange is preferred. , 12) A description of the operation of the VTI and magnet, including a diagram of the cooling circuit, should be provided. The process by which , measurement inserts are exchanged should be described, with particular emphasis on requirements, if there are any, for purity of gas that is , introduced into the sample space. It should be specified whether a liquid nitrogen cold trap is necessary for operation of the cooling circuit. , Maintenance and replacement schedules for parts required for operation of the cooling circuit should also be specified. The tenderer may also provide any further information pertinent to the long-term reliability and ease-of use of their system., 13) It is desirable that the gas pressure in the sample space can be varied; please specify if this is possible and if so how., 14) Sample space diameter of 50 mm or more., iv. General-purpose measurement insert, 15) 12 manganin twisted pairs. , 16) At least one free KF16 or KF25 flange, to allow user installation of additional , wiring. Two free flanges are desirable. (Here and on the other inserts: we anticipate running six coaxial lines, which may be flexible. If the supplier can provide inserts with these coaxial cables already installed, we will consider it, but it will not be a major factor in our decision. Flexibility to install additional cables of our own is important. ), 17) A free sample space of at least 70 mm below the field centre, and 120 mm above, with a diameter of at least 44 mm. Note that these are the same requirements as for the sample-in-vacuum insert. Note also that we are not looking for the supplier to provide specific solutions on sample mounting. We will manage this ourselves; what we want is flexibility., v. Sample-in-vacuum measurement insert, 18) 12 manganin twisted pairs. , 19) At least one free KF16 or KF25 flange, to allow user installation of additional wiring. Two free flanges are desirable., 20) An inner diameter of the vacuum can of at least 44 mm, 21) Free sample space of at least 70 mm below the field centre, and 120 mm above., vi. 3He insert, 22) 12 manganin twisted pairs. , 23) At least one free KF16 or KF25 flange, to allow user installation of additional , wiring. Two free flanges are desirable., 24) An inner diameter of the vacuum can of at least 44 mm, 25) Free sample space of at least 70 mm below the field centre, and 120 mm above., 26) With a 10 µW heat load, a hold time at a temperature of 320 mK or below of at least 24 h., 27) Please specify the type of temperature sensor and source of its calibration., vii. Higher-temperature option, 28) The tenderer should specify a method to achieve higher temperatures. If possible, this option should satisfy the sample space specifications given for the sample-in-vacuum interface. If it is not possible, options giving more sample space, up to these specifications, are preferred. The 400 K option may be achieved using one of the inserts listed above, or a separate high temperature insert. The preferred maximum temperature is 400 K, while holding the magnet at +12 T. No points will be awarded for temperatures above 400 K., viii. Ceiling height, 29) The system should be operable with a 3.7 m ceiling height.