Cryogen Free Dilution Refrigerator with 1T superconducting magnet

Cryogen Free Dilution Refrigerator with 1T superconducting magnet

The system is designated for measuring parameters of nanoelectronic-, single electronic- and nanomechanic- components at mK temperatures.  It consists of cryogen free dilution refrigerator BF- L D250 BlueFors with a pulsed tube  (Fig. 1).

Fig.1. Cryogen free cryostat BF- L D250 with a pulsed tube.

BF-LD250 Main parts:

1. Cryocooler – pulsed tube with compressor

2. Frame for the cryostat suspension;

3. Dilution refrigerator insert

4. Vacuum can and radiation shields

5. Control system of gas handling (He3/He4 mixture), including user interface, pressure gauges with electronic interface, circulation gauges, управляемые вентили и соединительные линии откачки;

6. External and internal nitrogen traps;

7. Temperature sensors (resistance thermometers) and heaters, are installed at the 1st и 2nd cooling stages, mixing chamber and still. Thermometer readings and  heaters control is used via hermetic  LEMO-connector at the cryostat top plate, connected to the  Lakeshore 370 controller with  16-channels scanner.

Designfeatures

The large space sample chamber (bottom of the mixing chamber) –250mm in diameter and 220mm height – enable various types of measurements. The mixing chamber is displaced off-center in order to enlarge the available sample space  (Fig.2).

Fig.2. Bottom view of the mixing chamber and available sample space.

The vacuum can of the cryostat and the system of thermal shields are made of aluminum for decreasing weight. It consists of two arts – upper and lower ones – that facilitates access to the sample chamber. For installing a sample, only lower parts of the can and shields are removed; usage of special lockers makes this operation possible by a single person with no additional lifting mechanisms (Fig.3).

Fig.3. Disassembled vacuum can and radiation shields system

Major technical parameters.

(a) Measuring microwave instruments  (from Agilent):

1. Frequency range from 10 MHz to 43.5 GHz  with a 0.001Hz resolution;
2. System dynamic range 126dB, Receiver dynamic range 129dB, 32001 points, 32 channels, Transmission bandwidth  at the intermediate frequency of  5MHz;
3. Maximal output power +16 dBm;
4. Dynamic resolution 0.1dB;
5. Minimal noise level -111dBm at  10 MHz IF bandwidth.

b) Cryogen free dilution refrigerator with pulsed tube BF- L D250 BlueFors:

1. Cooling power ~ 300mcWt (at 100mK);
2. Base temperature ~10mK; 
3. Sample chamber  - 250mm in diameter and  220mm height;
4. Sample environment  – vacuum;

1. Start-up time for achieving the base temperature  ~ 17h.