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Introduction to Semiconductor Photon Detectors
The invention of semiconductor photon detectors based on large cryogenically cooled germanium and silicon diodes began in the 1950’s. By the mid 1960’s, ORTEC was offering commercial lithium-drifted germanium, or Ge(Li) and lithium-drifted silicon or Si(Li) models. By the mid 1970’s high purity germanium, or HPGe, detectors had replaced the GeLi versions. Today ORTEC offers the widest range of semiconductor photon detectors up to very large crystal sizes.
These detectors are capable of very high energy resolution and since their invention have proved highly desirable in many applications, most recently in relation to homeland security, where an opponent in nuclear materials trafficking is trying to mislead a detection system into providing the wrong identification result. The “gold standard” in these measurements is considered to be a germanium detector.
Classically, cooling for germanium and silicon semiconductor photon detectors has been implemented by the use of liquid cryogens, most commonly liquid nitrogen. The requirement for such cooling has been a limitation to the deployment of these detectors. Since the mid 1980’s ORTEC has pioneered the use of mechanical coolers, at this date (2009) having delivered more mechanically cooled HPGe detectors than all other manufacturers combined.
ORTEC HPGE detectors are now in use world-wide in applications as diverse as nuclear structure physics and the prevention of illicit nuclear materials trafficking at the world’s largest ports of commerce.
More....
Germanium Detector Stocklist.
Tutorial of the Physics of Semiconductor Detectors [PDF]. |
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Silicon Charged Particle Detectors
 ORTEC introduced the first silicon surface barrier detectors for charged particle spectroscopy in the early 1960’s when the company was starting out. A broad product range to cover a wide variety of applications rapidly developed. Today there are no fewer than 13 product lines of semiconductor charged particle detectors available from ORTEC for such diverse applications as:
- Low background, high resolution alpha and beta spectroscopy of environmental and radiochemical samples.
- High resolution charged particle spectroscopy in nuclear physics, chemistry and space physics.
- Particle identification in time of flight telescopes.
- Particle backscattering.
- Heavy ion spectroscopy and time-of-flight.
- Medium-energy charged particle spectroscopy.
- Charged particle energy and position determination.
- High resolution beta spectroscopy.
Charged Particle Detector Data Summary and Selection Chart.
Charged Particle Detectors for Alpha Spectroscopy.
Charged Particle Detectors for Research Applications.
Charged Particle Detector Mounting Arrangements. [PDF]
Tutorial Information on Charged Particle Detectors. [PDF]
Scintillation Photon Detectors
 Spectroscopic Scintillation photon detector technology predates that of semiconductors by more than a decade. Nonetheless, these detectors continue to dominate from the standpoint of numbers in use, and the advent of new scintillation materials has improved their energy resolution significantly, although they are still on the order of 20 times poorer in resolution than HPGe detectors, but they have the great benefit of generally lower cost and the fact that they operate at room temperature.
As the name implies, a scintillation detector relies on the generation of light pulses by gamma-ray interaction, which are then detected in a photomultiplier, and converted to a voltage pulse for further signal processing. The most common spectroscopic scintillation detectors are based on thallium doped sodium iodide or NaI(Tl). More recently, detectors based on Lanthanum Halides have appeared offering ~2x improvement in energy resolution.
While ORTEC is not a manufacturer of Scintillation detectors, they are available from ORTEC along with an array of electronic and software products which them. NaI(Tl) detectors form a key component in many ORTEC Integrated systems, such as whole body counters and homeland security search systems.
More about Scintillation Photon Detectors.
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