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Calibration
of a Plasma Calorimeter
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New Updates |
Theoretical Simulation |
Preliminary Results |
We are developing a technique to calibrate the plasma calorimeters which are to be used as a diagnostic tool in studying nuclear fusion reactions at at the University of Rochester Laboratory for Laser Energetics (LLE). The calorimeters are being calibrated at the State University of New York at Geneseo Department of Physics and Astronomy by several students under the advisement of Dr. Charlie Freeman.
The
OMEGA 60 laser,
housed at the LLE is used to deliver a burst of more than 40,000 Joules
of energy to a target of less than 1 mm in diameter. This burst of energy
cases the atoms that the target is composed of to fuse and release thermal
and radiant energy in the form of a fusion plasma. The plasma calorimeters
are used to study the energy contained within the fusion plasma. Seventeen
plasma calorimeters are placed around the target area of the OMEGA 60 laser.
The calorimeter consists of two 6 micron thick tantalum foils placed side
by side (see
figure). The foils are 6 mm wide and 13 mm high. One foil is open to
the fusion plasma and the other is covered by a UV filter. Thermocouples
are mounted on the foils which measure the temperature of the foils relative
to a copper reference plate (DT2 and DT3).
An additional set of thermocouples is used to measure the temperature difference
between the right and left foil (DT1).
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Schematic of the plasma calorimeter |
Photograph of the plasma calorimeter |
These calorimeters are being calibrated at the Geneseo Nuclear Structure Laboratory (NSL). The calorimeters are placed in the back of a 2'x2' target chamber (see figure). A beam of monoenergetic protons of adjustable energy and intensity from the 2 MeV Van de Graaff accelerator strike the calorimeter. The beam can be deflected to a particular calorimeter foil by a pair of electrostatic deflector plates mounted in the target chamber. The energy deposited on the calorimeter foil is determined by the proton beam current which is measured via Rutherford Scattering. The three thermocouple signals are recorded as a function of time using the LabVIEW data acquisition and control software.
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Schematic of the 2'x2' chamber at the Geneseo NSL.A monoenergetic beam of protons strike the calorimeter foils, causing the foils' temperature to increase. The proton beam current is determined via Rutherford Scattering: A small fraction of the proton beam is deflected off the gold foil into a surface barrier detector. The beam current is extracted from measurements of the flux of protons into the surface barrier detector. A voltage difference is applied between the deflector plates in order to deflect the proton beam to a particular calorimeter foil. |
