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| Home > Publications database > Monte Carlo simulation of a mesitylene based cold moderator system foraccelerator-driven compact neutron sources |
| Abstract | FZJ-2022-01801 |
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2022
Please use a persistent id in citations: http://hdl.handle.net/2128/30954
Abstract: The organic compound mesitylene has been proposed as a suitable material for cold neutron generationalongside liquid ortho/para H2 and solid CH4 at cryogenic temperatures because it has a high hydrogendensity, enables a safe operation. To investigate the neutron moderation properties of mesitylene andits potential application in the High Brilliance Neutron Source (HBS) project, a mesitylene based coldmoderator system was set up in the Big Karl experimental hall at Forschungszentrum Jülich andperformed to determine the cold neutron spectrum at different moderator temperatures.In the experiment, primary neutrons are generated by the Ta(p,xn )W reaction using a pulsed 45 MeVproton beam and further moderated by polyethylene thermal moderator blocks. An extraction channelis built to gain the neutrons from the thermal maximum, and the cold mesitylene is placed in it. Themoderator vessel is a cylinder with a diameter of 60 mm and a height of 30 mm. The mesitylenemoderator system is cooled from 300 to 22 Kelvin by a cold finger cryocooler in about two hours. andmoderates the neutrons to a long wavelength of up to 40 Å. The moderated neutrons were extractedvia the flat side of the vessel and measured by TOF using a 7-meter neutron guide and 3He tubedetectors in TOF counter mode.Monte Carlo simulations of this mesitylene based cold moderator system were performed using theMCNP6.1 program package. The geometry for the simulation is converted from the three dimentionalCAD model of the experimental setup directly. The neutron spectra at different mesitylenetemperatures were calculated with respect to the gain of the cold neutrons compared to a spectrum atroom temperature. A broadening and shift of the cold moderator peaks to longer wavelengths withdecreasing moderator temperature is observed in both experimental data and simulation results. Whenthe mesitylene temperature decreases from room temperature to 22 Kelvin, the neutron spectrum peakshifts to a longer wavelength. Mesitylene has proven to be a proper moderator material for cryogenictemperatures around 20 K, which offers good performance.
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