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Table of Contents
Temperature Control
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).
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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.
