Diamond detector matrix

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Abstract

A 12-­‐pixels diamond based neutron spectrometer matrix has been built in a collaboration between the  two  CNR  institutes  IFP  (Institute  of  Plasma Physics,  Milan)  and  ISM  (Institute  of  the  Structure  of  Matter,  Rome).  The  spectrometer is equipped with fast electronics and digital acquisition, which for the first  time  allows  combined  fast  neutron  spectroscopy  (>1  MeV)  with  good  energy  resolution (<3% at 14 MeV) and high count-­‐rate capability in excess of 1 MHz.

Description of the Technology

A  12-­‐pixel  diamond-­‐based  neutron  spectrometer  matrix  has  been  developed  and  built in a collaboration between two Italian research institutes within the VNS enhancement  project.  This  new  spectrometer  allows  for  spectroscopic  analysis  of  fast neutrons to be undertaken where both a good energy resolution and high count-­‐rate can be achieved. Each pixel is made of a single crystal diamond of area 4x4x0.5 mm3 and is grown using the Chemical Vapor Deposition (CVD) technique.
The  diamond  matrix  will  be  used  to  take  high  energy  resolution  measurements  of  the 14MeV neutron spectra created in Deuterium-­‐Tritium plasmas within the JET tokamak.  Moreover,  the  diamond  matrix  is  also  capable  of  measuring  2.5  MV  neutron spectra from D plasma with limited energy resolution. Each pixel is completely independent of the others.
The new detector features the advantages of being compact, insensitive to magnetic field  and  radiation  resistant,  which  makes  it  ideal  for  use  on  neutron  cameras  of  future burning plasma experiments such as ITER or DEMO.
No patent has been made on this instrument.

Innovation and advantages of the offer

Fast  neutron  spectroscopy  with  combined  good  energy  resolution  (<3%  at 14MeV) and high count-­‐rate (in excess of 1MHz).
Compact
Insensitive to magnetic fields
Radiation resistant

Non-fusion applications

Currently  being  developed  for  use  on  JET  to  measure  neutron  spectra  from  DT  plasmas.
Applications  also  exist  at  spallation  neutron  sources  for  the  measurement  of  fast  neutron  beam  characteristics  (spatial  and  energy  distribution).  Due  to  the  typical  short‐pulsed  nature  of  the  beam  (width  in  the  range  1-­70ns)  these  measurements  require a spectrometer capable of handling a very high instantaneous count rate (>1 MHz)  and  spectroscopy  in  a  wide  energy  range  (from  10  MeV  up  to  hundreds  of  MeV).
The  diamond  matrix  can  also  be  developed  and  used  for  spectroscopic  analysis  of  charged particles, such as protons or alpha particles.
The  matrix  can  be  exploited  for  radiation  therapy  dosimetry.    The  single  pixel  can  operate  also  as  a  diamond  dosimeter,  with  advantages  connected  to  radiation  damage resistance, response linearity with radiation dose and dose‐rate, and tissue-­equivalent behavior (atomic number very close to the mean of human tissue). The matrix, mounted inside a water phantom normally used in radiation therapy, can be motorized  by  x-­y-­z  translational  stages  to  cover  large  areas  and  field  depth,  thus  allowing a real-­‐time, fast, and precise periodic calibration of the large radiation fields used in radiation therapy (i.e. dose-­rate distribution map), which is today performed with rougher and significantly less precise methods.
Finally, application could be foreseen in the field of security wherever a compact and portable detector is needed for detection of fast neutrons.

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