What is an HPGe detector?
Synopsis: High Purity Germanium (HPGe) is the only radiation detection technology that provides sufficient information to accurately and reliably identify radionuclides from their passive gamma ray emissions. HPGe detectors have a 20-30x improvement in resolution as compared to that of Sodium Iodide (NaI) detectors.
How does a HPGe detector work?
Under the influence of an electric field, electrons and holes travel to the electrodes, where they result in a pulse that can be measured in an outer circuit. This pulse carries information about the energy of the original incident radiation.
What is the importance of energy calibration of HPGe detection system?
HPGe gamma detector is used for analysis environmental samples in which calibration is very important. To acquire the function ship between efficiency and energy in wider energy range. About 10 standard sources are now wed worldwide, among which, five nucleus’ lifetimes are short.
Why Liquid nitrogen is used in the HPGe detector?
Cooling to liquid nitrogen temperature (-195.8°C; -320°F) reduces thermal excitations of valence electrons so that only a gamma ray interaction can give an electron the energy necessary to cross the band gap and reach the conduction band. Therefore, HPGe detectors are usually equipped with a cryostat.
What is the resolution of HPGe detector?
The detector has an energy resolution of 2.4 keV at 1.332 MeV (gamma ray from a 60Co) and a relative efficiency of 70% guaranteed in 1991.
How much does a HPGe detector cost?
For a 100% relative efficient HPGe detector system with mechanical cooling, the current price is on the order of $75,000.
What is the efficiency of a detector?
“Detection efficiency” is defined as the ratio of the output signals to incident electrons, X-rays or photons to a detector (input signals). A detector with high detection efficiency meets various requirements, such as high conversion efficiency from input to output, short dead time, and low noise.
How do you calculate the efficiency of a detector?
the efficiency of the detector for radiation from the sample must be calculated using formula ε(E) = ω ε0(E), finding the value of the coefficient ω for the relation (2). For a cylindrical container l = H and for a complex-shaped container l = H – h.
Why do HPGe detectors need to be cooled?
Germanium detectors must be cooled to reduce this leakage current to the point where the associated noise does not degrade the energy resolution. Normally, HPGe detectors are cooled with liquid nitrogen (LN2) to 85- 105 K inside a specially-designed cryostat.
Why is HPGe better than NaI detector?
The HPGe detector offers less detection efficiency compared to the NaI (Tl) detector. It means that, HPGe is efficient in detecting nuclides with lower energy but not nuclides at higher energy. Na(TI) detector is a more efficient detector compared to HPGe detector although it has a very poor resolution.
What is a HPGe detector?
4.1 Detector Structure Basically, a HPGe detector is a very large semiconductor diode, with a reverse bias voltage applied to its two electrodes to deplete virtually all free charge carriers from the bulk of the detector. Small detectors can be obtained in the planar geometry.
How to calculate the energy resolution of HPGe detector?
The energy resolution of HPGe detector is given by, E total= q ( E noise)2+ ( E ion)2+ ( E incomplete)2(9) where E ion= 2:35 p FE (10) E totalis the full width at half maximum amplitude (FWHM) of the gamma-ray peak at energy Ein the spectrum. E noiseis the contribution from the noise caused by the detector leakage current and the preampli\fer.
What is the charge collection time of an HPGe detector?
For large coaxial HPGe detectors the charge collection time can vary from 50 to 700 ns, depending on the position at which the charge was created. If the ampli\fer shaping time constant is not large compared to these collection times, the pulse height will show additional uctuations caused by random variations in the charge collection times.
What are the characteristics of HPLC detectors?
6. Detection in HPLC HPLC Detectors were common laboratory instrument ◦ Usually a narrow linear range Must be solvent -compatible, stable etc. Universal–Respond to all analytes Analyte Specific ◦ Respond to specific properties of analytes Non-destructive & Destructive 6 8.