To maintain stability ad sub-150K temperatures within the cryostaic volume, a mixed refrigerant Joule Thompson cooler combination with a PID driven heater / temperature sensor system is used.

=====ORCA Cryo-Cooler===== — The cryo-coller is an ORCA system, manufactured by Advanced Research Systems. The system is designed around a cooling cycle optimized to maintain temperatures of 90 K (-183.15 C) without the use of liquid cryogens. By exploiting the Joule-Thomson effect, the use of no moving parts within the cryo-head is achieved, resulting in a low vibration, orientation independent, operation with an air-cooled compressor. The system consists of two components: the air-cooled mixed refrigerant compressor (MRCM-150-2) with a 10.000 h maintenance cycle, and the ORCA-MR mylar wrapped cryo-head (MRCH-1). | | | The non-toxic MRSG-110 refrigerant is used in the system, allowing for minimum temperatures around 110K. Lower values may be achieved by transitioning to a different refrigerant which most possibly will require modifications to the compressor. The thermal capacity of different available refrigerants can be seen in the following plot: The cryogenic system features no power or thermostatic control. Temperature regulation is achieved with a mixture of programmable power control and heater elements implemented at the attachment interface of the cryo-head. ^ Compressor Specifications ||| | Power Usage | Frequency | 50 / 60 Hz | | ::: | Voltage | 220 - 240 V | | ::: | Power | 750 VA | | Dimentions | Length | 356 mm | | ::: | Width | 483 mm | | ::: | Height | 394 mm | | ::: | Weight | 36.3 kg | | Typical Maintenance Cycle || 10.000 h | =====Lakeshore Temperature Controller===== Since the cryocooler has no thermostat, we use a heater with sensors to keep our samples at the desired temperature. We use the LakeShore 335 Temperature Controller as the heater, which has a heating capacity of 75 W and works in a temperature range from 300 mK to 1505 K. It comes with two sensor outputs: one is used to measure the CCD temperature, and the other is used to measure the temperature of the cryohead. It is mounted to a rack next to the Keithley 2470 SourceMeter. We use a LabVIEW script to control the LakeShore remotely via the server. To control the cryocooler, we use a PDU, which itself is controlled via a LabVIEW script. The LakeShore 335 has two outputs with different output settings (for more Information Datasheet, Manual): ^ Outpout 1 |||| | Type | Variable DC current source ||| | Control Modes | Closed loop digital PID with manual output or open loop ||| | D/A resolution | 16-bit ||| | | 25 Ω setting || 50 Ω setting | | Max Power | 75 W* | 50 W | 50 W | | Max current | 1.73 A | 1.41 A | 1 A | | Voltage compliance (min) | 43.3 V | 35.4 V | 50 V | | Heater load for max Power | 25 Ω | 25 Ω | 50 Ω | | Heater load range | 10 Ω - 100 Ω ||| | Ranges | 3 (decade steps in power) ||| | Heater noise | 0.12 µA RMS (dominated by line frequency and its harmonics) ||| | Grounding | Output referenced to chassis ground ||| | Safety limits | Curve temperature, power up heater off, short circuit protection ||| * 75 W only available if Output 2 is in voltage mode. ^ Outpout 2 |||| | Type | Variable DC current source or voltage source ||| | Current mode || Voltage mode || | Control Modes | Closed loop digital PID with manual output, zone, open loop | Closed loop digital PID with manual output, zone, open loop, warm up, monitor out || | D/A resolution | 15-bit | 16-bit (bipolar)/15-bit (unipolar) || | | 25 Ω setting | 50 Ω setting | N/A | | Max Power | 25 W | 25 W | 1 W | | Max current | 1 A | 0.71 A | 100 mA | | Voltage compliance (min) | 25 V | 35.4 V | ±10 V | | Heater load for max Power | 25 Ω | 50 Ω | 100 Ω | | Heater load range | 10 Ω - 100 Ω || 100 Ω min (short circuit protected) | | Ranges | 3 (decade steps in power) || N/A | | Heater noise | 0.12 µA RMS || 0.3 mV RMS | | Grounding | Dual banana || Detachable terminal block | | Safety limits | Curve temperature, power up heater off, short circuit protection ||| =====Connection Layouts===== The connection protocoll between the AlpineCube outside and the LakeShore 335: ^ DB 50, Alpine Cube - Lakeshore ||||| ^ ^ Alpine Cube Side |^ Lakeshore 335 Side || | ::: ^ Function ^ Pin ^ Pin ^ Function ^ | Bottom Row | | 1 | x | | | ::: | | 2 | x | | | ::: | | 3 | x | | | ::: | | 4 | x | | | ::: | | 5 | x | | | ::: | | 6 | x | | | ::: | | 7 | x | | | ::: | | 8 | x | | | ::: | | 9 | x | | | ::: | | 10 | x | | | ::: | | 11 | x | | | ::: | Heater 1 | 12 | Lakeshore | Heater Output 1 | | ::: | ::: | 13 | ::: | ::: | | ::: | Temperature sensor 2 | 14 | Lakeshore | Sensor Input A | | ::: | ::: | 15 | ::: | ::: | | ::: | Temperatrue sensor 1 | 16 | Lakeshore | Sensor Input B | | ::: | ::: | 17 | ::: | ::: | | Middle Row | | 18 | x | | | ::: | | 19 | x | | | ::: | | 20 | x | | | ::: | | 21 | x | | | ::: | | 22 | x | | | ::: | | 23 | x | | | ::: | | 24 | x | | | ::: | | 25 | x | | | ::: | | 26 | x | | | ::: | | 27 | x | | | ::: | | 28 | x | | | ::: | | 29 | x | | | ::: | | 30 | x | | | ::: | Temperature Sensor 2 | 31 | Lakeshore | Sensor Input A | | ::: | | 32 | x | | | ::: | Temperature Sensor 1 | 33 | Lakeshore | Sensor Input B | | Top Row | | 34 | x | | | ::: | | 35 | x | | | ::: | | 36 | x | | | ::: | | 37 | x | | | ::: | | 38 | x | | | ::: | | 39 | x | | | ::: | | 40 | x | | | ::: | | 41 | x | | | ::: | | 42 | x | | | ::: | | 43 | x | | | ::: | | 44 | x | | | ::: | Heater 2 | 45 | Lakeshore | Heater Output 2 | | ::: | ::: | 46 | ::: | ::: | | ::: | Temperature sensor 2 | 47 | Lakeshore | Sensor Input A | | ::: | ::: | 48 | ::: | ::: | | ::: | Temperature sensor 1 | 49 | Lakeshore | Sensor Input B | | ::: | ::: | 50 | ::: | ::: | The AlpineCube uses a passage connector, which inverts the pin numbers, because it goes from a male to male connector. In the pictures below the schematics for each sides are made. * AlpineCube inside Take note that pin 1 is only connected to pin 34 and not directly connected to the sensor (analog for the pins 2,3 and 4). —- * AlpineCube outside Take note that the on this side each sensor uses 5 pins (Sensor 1 uses: 16,17,33,49,50), while on the inside of the AlpineCube they only use 4. —- ===== System output configuration ===== In this system we go with a Resistor 50 Ω 1% 60W to 220. Which sets the max power setting to 50 W and max current to 1 A.