Magnetic Proton Recoil neutron spectrometer is a large high-resolution neutron

spectrometer A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the ...

installed at

JET Jet, Jets, or The Jet(s) may refer to: Aerospace * Jet aircraft, an aircraft propelled by jet engines ** Jet airliner ** Jet engine ** Jet fuel * Jet Airways, an Indian airline * Wind Jet (ICAO: JET), an Italian airline * Journey to Enceladus a ...

History

The Magnetic Proton Recoil (MPR) neutron spectrometer is a thin-foil spectrometer which was installed at

in 1996 and upgraded (MPRu) 2001-2005.

Principle

In the MPR the fusion neutrons are collimated into a neutron beam. The neutron beam is directed onto a thin plastic film ( Polyethylene) where the neutrons scatter elastically on the

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

s of the foil. The recoil protons emitted in the forward direction enter a magnetic part of the spectrometer where they are momentum analyzed and focused onto the focal plane. An array of plastic

scintillator A scintillator is a material that exhibits scintillation, the property of luminescence, when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate (i.e. re-emit the absorbed ...

s coupled to

photomultiplier tube Photomultiplier tubes (photomultipliers or PMTs for short) are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum. They are members of the class of vacuum tubes, more specif ...

s (PMTs) register the spatial distribution of the protons. This proton distribution is then related to the neutron energy spectrum.

Field-of-view

The MPR has a semi-tangential line of sight through the

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

. The MPR has a 700 mm long cylindrical steel neutron collimator with a 10-cm2 bore. At a distance 170 mm behind the end of the collimator is placed a 10 cm2 polythene conversion foil, defining the active area of the spectrometer. The collimator-foil arrangement defines the spectrometers field-of-view into the plasma.

Uses

The MPR determines the neutron spectrum from which important plasma parameters can be determined, such as the ion temperature, the collective motion of the main plasma, the fuel ion densities and their velocity distributions.

References

{{reflist}
The thin-foil magnetic proton recoil neutron spectrometer MPRu at JET
Tokamaks Neutron facilities Spectrometers

History

Principle

Field-of-view

Uses

See also

References