Instrumentation and auxiliary equipment

Posted by Rezwan on Aug 03, 2009 at 12:49 AM
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LPP has received our most economical complete scientific instrument, an x-ray pinhole camera costing only $67. (Our most expensive single instrument, not yet received, is the $65,000 ICCD camera, with an exposure time of 0.2 ns). The pinhole, 25 microns in diameter in a 25 micron thick sheet of copper, will allow us to make images of the plasmoid in relatively soft x-rays of 10 keV or less. While harder x-rays, probably most of the energy, will pass through the copper film, the image formed by the pinhole should have sufficient contrast (around 10%) to be easily measurable. The resolution should be adequate for the larger plasmoids in deuterium. The pinhole images will allow us to see the location and variability in location of the plasmoid. This will let us decide the best alignment for the x-ray lens, which will be able to obtain higher-resolution images of the hard x-ray emission, but with a much smaller field of view.

Our other instruments are still being assembled. For the x-ray detectors, and neutron time-of- flight detectors, we have ordered the photomultiplier tubes (PMTs), amplifiers and power supplies. We have also ordered the triaxial cable that will connect the x-ray detectors, through a conduit under the wall, to the oscilloscopes. Triax cables have an extra layer of conductor to serve as a shield against RF noise. This shield will be grounded to the copper mesh that surrounds the experimental room. The detectors themselves will be inside copper tubes attached to the triax shield, so will be shielded against the RF noise that the DPF generates.

We have received silver foil and ordered PMTs to build a type of silver activation neutron detector that has been previously tested and calibrated. In this detector, neutrons from the device will be slowed by polyethylene moderators and absorbed by the silver, creating very short-lived radioactive species. These isotopes emit electrons, beta-rays, that then excite photon emissions in layers of plastic scintillators. These in turn are detected the PMTs. While seeming complicated, this is the most reliable way to measure total neutron emission.

We will be further calibrating these two detectors with a calibrated neutron source. Since this is a radioactive source, although a small one, we require a license for it and we have applied for one to the State of NJ.