Low vibration helium bath cryostat with sample in exchange gas: OptistatSXM

OptistatSXM high stability liquid helium bath cryostat

This high stability helium bath cryostat is ideal for low-vibration optical spectroscopy and nano-scale microscopy and applications requiring:

Wide temperature range from 1.6K to 300K
Excellent control and stability of the sample temperture using the dynamic exchange gas principle
Low vibration note 1 designfor applications requiring high levels of mechanical stability including Scanning Probe Microscopy (SPM), Near-field Scanning Optical Microscopy(NSOM), Scanning Tunelling Microsopy (STM) and Atomic Force Microscopy (AFM). The large sample space(49 mm) enables the integration of probe heads
Quick sample change in less than 5 minutes
Efficient cryogenic design provides the convenience of consistent low temperature operation over a working day
Generous optical access (f/2.2) for the radial windows
Versatile: wide range of sample holders/rods including liquid cuvette for liquid samples and simple/precise height adjust/rotate sample rod
Electrical measurements via 10 pin connector or wired coax connectors

Note 1: Low vibration design : this cryostat uses the exhausting helium gas from the helium reservoir to cool the radiation shielding, thereby minimising the helium consumption. This eliminates the need for for a nitrogen reservoir to cool the radiation shield , which would be a source of vibration due to the boil off of liquid nitrogen.

Specifications
System components/options
Operation
Applications
Images

Sample space diameter (mm)	49 mm
Temperature range (K)	4.2-300 K (with GF4 pump) 1.6-300 K (with EPS40 pump)
Temperature stability (K)	+- 0.1K using an ITC controller (measured over 10 min period)
Liquid helium reservoir capacity (L)	4L
Hold Time at 4.2 K (hours)	>= 10
Sample change time (mins)	5
Optical access	f/2.2 for radial windows

A typical OptistatSXM system consists of:

OptistatSXM
Sample rod and holders
Up to five sets of windows. (four radial; one axial). Each set includes three windows (indium sealed inner window, radiation shield and outer case windows). As standard two of the windows are fitted with Spectrosil B windows and the remaining windows are fitted with blanks.
MercuryiTC temperature controller
Gas flow pump
High vacuum pumping system
Cryogen transfer tube

Optional items:

Wiring and electrical connections to the sample: eires may be terminated at pins above the the sample holder and/or wired coax connectors.

Windows

The standard system is supplied with 2 radial windows fitted with Spectrosil B with the others blanked off
A wide range of window materials can be fitted to the OptistatSXM to meet specific spectroscopy applications
Special windows with non-parallel faces and anti-reflection coatings are available
Additional or replacement windows are available via the Oxford Instruments Direct - Cryospares® on-line catalogue

Pump options

A simple oil-free vane pump is supplied for operation to 4.2 K
Lower temperatures to 1.6 K require a single stage rotary pump (EPS40)

Temperature control and options

Cryostat system includes the new MercuryiTC cryogenic temperature controller.

Automated operation:

If the cryostat is fitted with an auto needle valve, the MercuryiTC can be used to to optimise the helium flow rate automatically and allow automation over most of the operating temperature range.

Software control

Oxford Instruments electronics products are controllable through the OxSoft software using RS232, ISOBUS or GPIB interfaces
LabVIEW virtual instruments are provided for Oxford Instruments electronics products to allow full PC-based control and monitoring. These can be integrated into a complete LabVIEW data acquisition system

The OptistatSXM cryostat contains an integral liquid helium reservoir with a variable temperature insert (VTI) and radiation shields cooled by the evaporating helium. In the OptistatSXM, the sample is in a dynamic exchange gas environment, meaning that the cryogen flows into the sample space cooling the sample directly.

Liquid helium is supplied from the reservoir to the VTI through a needle valve, allowing the flow to be optimised to suit the operating requirements. A heat exchanger at the bottom of the sample space is fitted with a heater and temperature sensor, so that the temperature of the helium flowing through the sample space can be controlled by a temperature controller. This helium then flows over the sample and out of the cryostat to a small vacuum pump, which is used to promote the flow and obtain temperatures below 4.2 K.

The sample is mounted on a sample rod and loaded into the cryostat through a NW50 flange. Changing the sample simply involves removing the sample rod, replacing the sample and inserting the rod back into the cryostat.

1.6 K operation:

This can be achieved either in continuous flow or single shot mode, using a large displacement pump ( typically 25 m3/hr). In single shot mode, the sample spcae is filled with liquid helium and pumped enabling a base temperature of 1.6 K. Base temperature will be maintained until all the liquid helium in the sample space has evaporated.

Scanning Probe Microscopy (SPM), Near-field Scanning Optical Microscopy (NSOM), Scanning Tunelling Microsopy (STM) and Atomic Force Microscopy (AFM).

Optical spectroscopy.

Case study:

An Opttistat SXM in the 'Spectrometrie Physique" laboratory (Grenoble University/CNRS/CEA) is used to produce single photons from individual semiconductor quantum dots. Singke photons are used in quantum information processing such as quantum cryptography.