NPL-2611 Secondary Standard Therapy Dosimetry Chamber

The NPL Chamber comprises a thin walled high purity graphite thimble, amber insulator and a hollow pure aluminum
electrode. It is supported by a thin walled aluminum stem which terminates into a robust cable entry which is used for
mounting the chamber. The chamber is connected to 10m low noise Triax cable terminating in a Triax BNC plug with a converter to Triax TNC
Key Features:
  • Air Vented Chamber– so air density corrections are to be applied
  • The chamber is manufactured in the UK by the National Physical Laboratory (NPL)
  • Maintenance and Calibration are carried out by the NPL
  • Secondary Standard calibrations for Electrons and Photos are carried out normally twice per annum and are  available directly from NPL


Download the datasheet:  NPL2611.pdf

To Get a Quotation click here           

Active Dimensions
Sensitive Volume—325mm3
Length of volume—9.22mm
Thimble wall thickness– 0.5mm
Diameter—7.35 mm
Exterior Dimensions
Length— 185mm
Diameter—12.5 mm
Thimble -high density (1.80b/cm3 high purity extruded graphite
Collecting electrode- aluminium 99.99% pure
Main insulator—PEEK
HV insulator– PEEK
The chamber stem is guarded to a point 15mm from the measuring volume
Reference Point
The effective measurement point for positioning the chamber should be taken to be the axis of the chamber 5mm from the tip of the graphite thimble
To ensure that the chamber is equilibrated with the atmosphere the measuring volume is vented giving pressure equilibration times for just a few seconds
Build up Cap
Delrin, with external diameter of 17.0 mm and wall thickness of 600mg/cm2
Suhner GO 233OHT connections
Centre core—signal at HV
Inner screen—guard at HV
Outer screen—earth potential
Length 10m
Energy response uniform +/- 1% from 1.0mm AL 20mm AL HVL (0.030mm Cu to 4.00mm Cu HVL )
Sensitivity 11nC/Gy nominal. Better than +/- 0.35 over 3 years
Polarising potential +/-200V / Max +/-400 V DC
Collection efficiency ( HV@-200V) continuous radiation better than 99.9% for dose/pulse values less than 43.5 microGy
Leakage better than +/-2X10E-14A
  • NPLSL - Water Proof Sleeve( one delivered with each new chamber)
  • NPLCDC - Sleeve to accommodate NPL-2611 into IBA CDC Check Source
  • NE2566A - Perspex Phantom for Intercomparison between Farmer Type and 0.33cc Secondary Standard