Ultra-low temperature facility

Full name:

Dilution refrigerator BlueFors LD250


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- LD250 BlueFors with a pulsed tube.

Technical specifications:

Cooling power~ 300 uW (at 100 mK)
Base temperature~ 10 mK
Sample chamber sizediameter – 250 mm & height – 220 mm
Sample environmentvacuum
Start-up time for achieving the base temperature~ 17 h

Main research directions:

  • Transport mesurements of new quantum and topologically non-trivial materials in magnetic field;
  • Investigating multiparticle states in supercondactors at ultralow temperature using upper critical field measurements;
  • Рighly correlated and low-dimentional systems at ultralow temperatures.

BlueFors 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;
  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.
Fig. 1. Cryogenfree dilution refrigerator

Design features:

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).

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).

Major technical parameters of easuring microwave instruments (from Agilent):

Frequency range from 10 MHz to 43.3 GHz (0.001 Hz resolution)
System dynamic range126 dB
Receiver dynamic range129 dB
Maximum output power+16 dBm
Dynamic resolution0.1 dB
Additional32001 points / 32 channels