Measurement Solutions for Nuclear Safety, Security and the Environment

Cryostats, coolers & options

Products in category

Electrically-cooled Cryostats

Electrically-cooled Cryostats

Description

CANBERRA's two electrically-cooled cryostats eliminate the need to constantly refill HPGe detector LN2 Dewars. This means less hassle, enhanced safety and a time-consuming chore crossed off your "to-do" list.

Cryo-Cycle II Hybrid Cryostat

Our Cryo-Cycle™ II "Hybrid" Cryostat has a 25-liter LN2 reservoir for continued operation in case of power failure — it can typically operate for over a year before adding more gaseous or liquid nitrogen.

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Cryo-Cycle™ II "Hybrid" Cryostat

Cryo-Pulse® 5 Plus Electrically Refrigerated Cryostat

Our compact Cryo-Pulse® 5 Plus Electrically Refrigerated Cryostat employs only electrical cooling and requires no LN2.

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Cryo-Pulse® 5 Plus Electrically Refrigerated Cryostat

Slimline Cryostats

Slimline Cryostats

Description

CANBERRA Slimline cryostats are designed so that the detector and electronics both fit in a cylindrical housing without any protruding flanges, valves, and preamplifier enclosures.

This compact configuration facilitates integration into shields and systems. Maintenance or exchange of the preamplifier is also very simple as it is located underneath the cylindrical cover, outside of the cryostat vacuum.

Vertical Slimline Dipstick cryostats can be fitted with a Remote-Detector Chamber (RDC). This RDC option separates the detector chamber from the Dewar and preamplifier and allows the use of a backshield so the lead shield completely surrounds the detector element.

Additionally the offset between the centerline of the RDC element and the cryostat coldfinger removes any direct "line-of-sight" between the detector chamber and the molecular sieves.

This design significantly reduces the radiation background on the detector. Standard lengths for the RDC option are 2, 4, 6, 8 and 10 inches. Custom lengths are available upon request.

End cap dimensions depend on detector size. The chart below shows the typical efficiency range vs. end-cap diameter. End cap lengths are also greater for larger detectors. Consult the factory if end-cap size is critical in your application.

Rel. Efficiency (%) Diameter in. (mm)
≤40 3.0 (76)
40-50 3.25 (83)
50-70 3.50 (89)
70-100 3.75 (95)
≥100 4.0 (102)
     
Flanged Cryostats

Flanged Cryostats

The liquid nitrogen cryostat is the most important and least appreciated component in assuring reliable long term performance of a germanium detector system. CANBERRA manufactures its own cryostats to exacting quality standards to ensure long detector life.

There are two basic types of cryostats in use: the dipstick, in which the detector occupies a vacuum chamber having a dipstick-like tail which is inserted into the neck tube of a Dewar, and the integral, in which the detector chamber and Dewar share a common vacuum.

The standard configuration comes with a radial O-ring seal. A metal face seal is available as an option on detectors with a 3.0 in. (76 mm) diameter endcaps only. Metal seals are more rugged and, in general, provide a longer life time of the detector vacuum.

Flanged cryostats can be fitted with a Remote-Detector Chamber (RDC). This RDC option separates the detector chamber from the Dewar and preamplifier and allows the use of a backshield so lead shielding that completely surrounds the detector element can be installed.

This significantly reduces the radiation background on the detector. Standard lengths for the RDC option are 2, 4, 6, 8 and 10 inches. Custom lengths are available on request.

End cap dimensions depend on detector size. The chart below shows the typical efficiency range vs. end-cap diameter. End cap lengths are also greater for larger detectors. Consult the factory if end-cap size is critical in your application.

Rel. Efficiency (%) Diameter in. (mm)
≤40 3.0 (76)
40-50 3.25 (83)
50-70 3.50 (89)
70-100 3.75 (95)
≥100 4.0 (102)
     
Portable Cryostats

Portable Cryostats

Description

For applications requiring both portability and flexibility of use, the MAC (multi-attitude cryostat) is the answer. The unique fill and vent system employed by the MAC allows operation of the detector in any orientation without LN2 spillage even when the Dewar is full. The small size, light weight, and ruggedness of the unit permit use of the unit in field conditions. The slimline detector chamber allows the unit to be shielded very effectively for use in low level counting applications.

The MAC detector consists of a Dewar having two fill and vent ports arranged so that one of the ports is the vent, regardless of the Dewar's orientation. This allows the Dewar to be operated in the horizontal position, vertically uplooking, or vertically downlooking, without loss of LN2.

A single port version of the MAC and Big MAC is available on special order. This version has half the capacity and holding time of the standard product. A gravity-feed supply Dewar/stand is available for the single port cryostat. The single port cryostat is compatible with other brands, and it holds LN2 in all orientations which may be important in some applications, e.g. for use in a submarine (see CANBERRA Model 7411).

The detector/preamp includes a sensor which provides a signal when the LN2 is depleted. This output can be used to shut down the bias supply, to operate an alarm, or both.

Features

  • Operation in any orientation
  • Light weight aluminum construction
  • Slimline detector/preamplifier configuration
  • Long holding time
  • Warm-up sensor-bias disable

Portable Cryostat

The standard MAC features CANBERRA's slimline cryostat option in which a CANBERRA preamplifier is packaged behind the detector chamber within the confines of the 80 mm diameter snout. The slimline cryostat allows the detector to be installed in a shield with very little difficulty and with efficient use of shielding material. The snout is long enough to reach through 10-15 cm of shielding material and still accommodate Marinelli beaker samples.

A flanged version of the MAC is also available. This version makes use of a conventional box style preamplifier having bulkhead connectors (rather than pigtail connectors) and is somewhat more compact than the slimline version.

The MAC comes with detachable carrying handle assembly. With the carrying handle assembly removed, there are no obstructions beyond the outer diameter of the Dewar, and the unit can be readily installed in other scientific apparatus such as whole-body counters, scattering chambers or low-level counting systems.

Both manual and automatic refill systems are available for use with the MAC. Since the MAC has separate fill and vent ports, the LN2 supply and the vent lines can be made gas tight, thus avoiding the hazards of cold N2 or LN2 to either personnel or adjacent equipment.

The MAC is available as an option with most of the High Purity Germanium detectors offered by CANBERRA. Consult the CANBERRA Catalog for information on the wide variety of detectors that are available from CANBERRA.

Retractable Cryostats

Retractable Cryostats

Description

These retractable cryostats from CANBERRA are used with Si(Li), LEGe, and Ultra-LEGe detectors in x-ray applications. Retractable cryostats provide a means of moving the detector element in relation to the sample with both under vacuum. They also make it possible to operate the detector in windowless mode, i.e. without a window (absorber) between the detector element and the sample.

As with any detector that is not permanently sealed, care must be exercised in using windowless detectors to avoid contamination of the detector element. The vacuum chamber to which the detector is attached must be clean and dry and under good vacuum before the gate valve is opened. Under no circumstances is the detector to be exposed to atmosphere while it is cold. Damage to detectors caused by contamination is not covered under warranty.

Features

  • Variable geometry
  • Windowless operation
  • UHV compatible
  • Rugged and reliable
  • Use with Si(Li) or Ge detectors

 

LN2 Gauge/Controller Model 7185/7186

LN2 Gauge/Controller Model 7185/7186

Description

The Model 7185 LN2 Level Gauge provides a digital display of LN2 level in a Dewar or container along with adjustable low and high level setpoints which initiate audible and visible alarm signals as well as a relay output for remote monitoring. The display shows liquid level from 0-100% of the active sensor length. It can be programmed to read out in inches or centimeters. Sensors are designed, sized, and configured for CANBERRA dipstick and integral cryostats. For portable cryo-stats refer to the Model 2541 Controller. Consult the factory for applications involving non-CANBERRA cryostats.

The Model 7186 provides the same functions as the 7185. In addition it has adjustable low and high level control setpoints and a relay which provides line voltage to a controlled ac output for operation of a solenoid valve. The control and alarm setpoints are readily adjustable by means of front panel controls. Setpoints are stored in non-volatile memory. This ac outlet is powered from the time the low setpoint is reached until either 1.) the high setpoint is reached or 2.) the user-programmed time-out is reached. The 7186 includes a cryogenic solenoid valve as well as fill and vent hoses. LN2 supply containers are available from CANBERRA for a complete automatic LN2 Fill System.

Both models operate on line voltage of 100, 115, 200, or 240 V ac, 50 or 60 Hz, internally selected. This line voltage is provided on the controlled ac outlet.

The 7186 Controller requires a source of LN2 at a pressure of 34 to 172 kPa gauge (5 to 25 psig). CANBERRA D-160 and D-240 containers or their equivalents are highly recommended. A self-pressurizing withdrawal device (NTD-30/50) with a 30 or 50 liter Dewar can be used but it is not highly recommended because of marginal capacity and pressure for most applications. The liquid quality must be good at the point of consumption. This means there must be no ice in the liquid and that the supply line must not be lossy (causing excess vaporization).

An overflow container may be required if there is no safe place for the discharge of overflow gas and liquid. WARNING: Malfunctions can result in the entire contents of supply containers being dumped through the system. CANBERRA takes no responsibility for such accidents. The user is responsible for the installation and for the safety measures that are needed in this application.

Features

Models 7185 and 7186

  • Digital level display
  • High and low alarm setpoints
  • Audible and visible alarm
  • Alarm relay
  • Sensor tailored to cryostat

Model 7186 Only

  • High and low control setpoints
  • Controlled ac output
  • Solenoid valve with captive 3 m (10 ft) cord
  • Hoses for fill and vent

Model 7185

Detector LN2 Monitor Model 1786A

Detector LN2 Monitor Model 1786A

Description

The Model 1786A Detector LN2 Monitor protects LN2-cooled detector systems against accidental warmup by monitoring liquid level in the Dewar and providing audible and visual warning of low liquid levels. It provides a signal for remote shutdown of Detector Bias Supply which has an Inhibit input. This singlewidth NIM module is suitable for most dipstick and integral type cryostats, but is not suitable for portable cryostats.

When your LN2 sensor detects a problem, the LN2 Monitor has provisions for turning off high voltage when an alarm condition occurs to protect detectors and electronics from damage. Shutdown does not occur until at least 20 minutes after the condition is sensed, and well before total depletion of the liquid nitrogen, so ongoing experiments can continue without interruption.

The Model 1786A must be manually reset following a power interruption. This will prevent HV Bias from coming on automatically (and abruptly) when the power is restored.

Features

  • Automatic protection against accidental detector warmup
  • Delayed shutdown saves experiments
  • Audible, visual and contact closure outputs

Model 1786

LN2 Accessories

LN2 Accessories

Model D-2 LN2 Fill Device

  • Self-pressurizing device for filling portable cryostats
  • Uses non-pressurized LN2
  • Capacity - 2 liters
  • Two charges fill MAC, 5-6 charges fill Big MAC

Model D-160 LN2 Storage Tank

  • 160 liter capacity
  • 152 kPa (gage) (22 psig) relief
  • 1.5% per day loss rate
  • Diameter - 51 cm (20 in.)
  • Shipping weight 100 kg (220 lb) empty

Model D-30; D-50 LN2 Storage Dewar

  • LN2 capacity (liters) -30/50
  • Diameter - 43 cm (17 in.)
  • Height - 61.5/89.4 cm (24.2/35.2 in.)
  • Loss rate (liters per day) - 0.5/0.6
  • Shipping weight 11.8 kg (26 lb)

Model NTL-6 Nitrogen Transfer Line

  • Insulated latex transfer line
  • 3/ 8 in. ID x 1/ 8 in. wall x 6 ft long

Model D-30/OS Offset Neck Dewar

  • Provides horizontal offset to detector chambers
  • Neck to be offset by 12.7 cm (5 in.)
  • Replaces D-30 Dewar in dipstick cryostats

Model D-240 LN2 Storage Tank

  • 240 liter capacity
  • 152 kPa (gage) (22 psig) relief pressure
  • 1.0% per day loss rate
  • Diameter - 66 cm (26 in.), height - 1.63 m (64 in.) (with casters)
  • Shipping weight 122 kg (270 lb), empty

Model NTD-30; NTD-50 LN2 Withdrawal Device

  • NTD-30 for use with D-30
  • NTD-50 for use with D-50
  • Pressure gauge
  • 34.5 kPa (gage) (5 psig) relief valve
  • Manual LN2 valve
  • Shipping weight 2.7 kg (6 lb)

Model RB-1 Roller Base for D-30 or D-50

  • Adjustable
  • Stable four-wheel design
Low Background Detector Systems

Low Background Detector Systems

Introduction

The term "low background" is used fairly indiscriminately in describing gamma analysis systems. The one common denominator for such systems is some form of shielding, but beyond this, anything goes. To bring some order to our own product line and to help customers distinguish the classes of systems, CANBERRA has chosen to categorize low-background gamma analysis systems as follows:

Low-Background

Ge detectors in a variety of cryostat types with lead shielding of 2-4 inch (5-10 cm) thickness. The only cryostats specifically excluded from this class are modular (convertible) types in which the molecular sieve adsorber is necessarily located near the detector element.

Ultra Low-Background

Ge detectors in cryostats that are A: designed for shielding effectiveness and B: constructed from materials that are notably low in background. The complementary lead shields are also made from select, low-background materials and are at least 4-6 inches (10-15 cm) thick. CANBERRA uses the term Ultra Low-Background to describe standardized detectors and shields which are described in the following pages. These standard products offer performance normally associated with much more expensive custom systems.

See more information on the Ultra Low-Background Cryostats (ULB) section that follows (or click here).

Specialty Ultra Low-Background

Systems in this class are designed for the specific application at hand. This type of system usually involves user specified design and/or performance criteria and close collaboration between the user and CANBERRA throughout the project - from inception to installation.

It is this class of system where active shielding (cosmic guards or Compton suppression) is often used. CANBERRA has a wealth of experience in building such systems and we welcome your inquiries should standard Low Background or Ultra Low-Background systems not satisfy your needs.

Read more in our Application Note entitled Ultra Low-Background Detector Systems for more information.

Typical Results

The following 50 000 second background spectra were taken with detectors having 100% relative efficiency. Spectrum A was taken without shielding. Spectrum B was taken with the detector in a standard cryostat (7500SL) operating in a standard 4 in. thick Lead Shield (747). Spectrum C was taken with the detector in an Ultra Low-Background Cryostat (7915-30 ULB) operating in a 15 cm (6 in.) thick ULB (Model 777) Lead Shield.

Comparative Background Counts are given below:

  Without Shield Standard Cryostat and Shield ULB Cryostat and Shield
Total Counts/Sec (50-3000 keV) 142.33.351.84
Peaks Found783113

Of the thirteen peaks found in the spectrum from the ULB system only one, the 2.614 MeV peak from Tl -208 is a normal background line. All the rest are attributed to cosmic ray interaction in the shield and detector.

A listing of these peaks and their means of production is given below:

Energy (keV) Isotope/Origin Remarks
53.473mGe 72Ge (n,g)
66.773mGe72Ge (n,g) (sum 13.3 & 53.4 keV)
139.775mGe74Ge (n,g
198.471mGe70Ge (n,g) (sum 174.9 & 23.4 keV
511Positron ann.Doppler broadened
569.7207Pb (n,n')Originating from stable Pb
in shield
595.874Ge (n,n')Broad assymetric, due to recoil summation
669.663Cu (n,n')
691.072Ge (n,n')Broad assymetric, due to recoil summation
803.1206Pb (n,n')Originating from stable Pb
in shield
834.072Ge (n,n')Broad assymetric, due to recoil summation
962.163Cu (n,n')
2614.5208TlIntensity about 0.1% of that of unshielded detector-believed to be shield penetration

Note: The fast and thermalised neutrons are of cosmic origin.

Ultra Low-Background Cryostats (ULB)

Ultra Low-Background Cryostats (ULB)

Description

CANBERRA has years of experience in building custom low-background detectors for low level gamma spectroscopy. The most important features of these custom detectors have been incorporated into standardized cryostat designs which can be produced quickly and economically and which produce predictable results. There are two basic Ultra Low-Background cryostat designs available, a vertical dipstick and a U-style integral. Both have the following design and construction features in common:

  1. Low background materials are used for detector chamber, holder, and internal hardware.
  2. Design offsets are used to allow the use of shielding materials between the detector element and hotter materials such as the preamplifier and adsorber (molecular sieves).
  3. Direct streaming paths for external (to shield) sources of radiation are eliminated.
  4. Materials having high cross-section for cosmic neutrons are avoided in construction.
  5. Designs do not compromise ease of use or long-term reliability.

Among the select materials used in CANBERRA ULB cryostats are the following:

  • Aluminum - 99.999% pure with guaranteed thorium and uranium less than 1 ppb.
  • Copper - 99.99% pure (better than standard OFHC grade).
  • Stainless Steel - selected low Co-60 content.
  • Composite Carbon - Virtually zero background substitute for Be in low energy and wide range detectors.

Features

  • Low background materials
  • No-stream-path design
  • Offset preamplifier and adsorber
  • Standardized hardware
  • Uncompromised reliability

Ultra Low-Background Cryostats (ULB)

U-Style Cryostats

U-Style Cryostats

Description

CANBERRA U-Style cryostats have a vertically-oriented detector chamber located at the end of a horizontal arm extending from the side of the Dewar or cooler.

This configuration excludes the preamplifier and other hardware from the inner cavity of the lead shield and eliminates all line-of-sight streaming paths to the detector element. These features contribute significantly to the overall background reduction of the counting system.

The U-Style configuration has a lower center of gravity for the detector and shield as compared to a standard vertical configuration which may make it attractive for mobile applications as in trailer- or ISO container-based counting facilities. Additionally the U-style configuration allows installing the detector in systems where there is no room under the shield to place the Dewar or cooler.

 

The standard length of the horizontal arm is 12 in. (305 mm) measured from the flange of the preamplifier service body to the detector center line. This length makes the U-style cryostat compatible with both 4 in. (102 mm) and 6 in. (152 mm) thick CANBERRA lead shields.

The standard configuration comes with a radial O-ring seal. A metal face seal is available as an option on detectors with a 3.0 in. (76 mm) diameter endcaps only. Metal seals are more rugged and, in general, provide a longer life time of the detector vacuum.

End cap dimensions depend on detector size. The chart below shows the typical efficiency range vs. end-cap diameter. End cap lengths are also greater for larger detectors. Consult the factory if end-cap size is critical in your application.

Rel. Efficiency (%) Diameter in. (mm)
≤40 3.0 (76)
40-50 3.25 (83)
50-70 3.50 (89)
70-100 3.75 (95)
≥100 4.0 (102)
     

Description

CANBERRA offers the broadest range of cryostat types in the industry. While some cryostat types are restricted for use with specific detector types, others can be used with all types of detectors.