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).

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			Cryo-Cooller Specifications
Power Usage	Frequency	50 / 60 Hz	Model	MR-90	MR-110	MR-125
	Voltage	220 - 240 V	Base Temperature	< 90 K	< 110 K	< 125 K
	Power	750 VA	Maximum Cylinder Temperature	355 K
Dimentions	Length	356 mm	Cooldown Time	~3 hrs (to base temperature)
	Width	483 mm	Weight	7.1 kg (Expander)
	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
	Heater 1	13	Lakeshore	Heater Output 1
	Temperature sensor 2	14	Lakeshore	Sensor Input A
	Temperature sensor 2	15	Lakeshore	Sensor Input A
	Temperatrue sensor 1	16	Lakeshore	Sensor Input B
	Temperatrue sensor 1	17	Lakeshore	Sensor Input B
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
	Heater 2	46	Lakeshore	Heater Output 2
	Temperature sensor 2	47	Lakeshore	Sensor Input A
	Temperature sensor 2	48	Lakeshore	Sensor Input A
	Temperature sensor 1	49	Lakeshore	Sensor Input B
	Temperature sensor 1	50	Lakeshore	Sensor Input B

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.

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Table of Contents

Temperature Control

ORCA Cryo-Cooler

Lakeshore Temperature Controller

Connection Layouts

System output configuration

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Table of Contents

Temperature Control

ORCA Cryo-Cooler

Lakeshore Temperature Controller

Connection Layouts

System output configuration

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