Abstract
In this contribution, we present the CoolGAL fast neutron production target system, to be used in the initial phase of the NEPIR irradiation beamline at the SPES facility, that will be operational in 2022. Initially, NEPIR will be used for shielding studies against fast neutrons for space applications and to investigate neutron-induced single event effects in microelectronic devices and systems. In CoolGAL, the neutron production component, a thick Be cylinder, is immersed in a static bath of Galinstan, a liquid alloy of Ga, In and Sn, contained by an outer water cooled copper cladding. MCNPX calculations indicate that, by using a 1 μA current of 70 MeV protons, it can produce a fast neutron energy spectrum that is somewhat flat the 30-65 MeV energy range and with a sharp cut-off at the beam energy. At the standard test point, located 2.6 m downstream from the source, the beam spot diameter, defined by the peculiar collimation scheme of the initial phase of NEPIR, is 10 cm and the integral fast neutron flux is Φn(1< En<65 MeV) ~ 3×106 n cm-2s-1. Using proton beams with two different energies, one can calculate, by subtraction, the effects due to the neutrons in the energy interval defined by the two cut-off values. Preliminary results of ANSYS calculations, for a 1 μA proton current of 70 MeV protons (70 W), show a limited regime temperature (28 °C) of the Be component, capable of ensuring the exceptional safety level required for the operation at SPES. The thermal reliability of CoolGAL is very promising for future developments that require higher proton currents.
Highlights
NEPIRNEPIR (NEutron and Proton IRradiation facility) is a multidisciplinary project at the new 30-70 MeV cyclotron of SPES [1] at the INFN National Laboratories of Legnaro (LNL)
It will deliver complementary fast neutron beams: quasi mono-energetic neutron (QMN) beams in the 30-70 MeV energy range and an intense neutron beam, with a continuous energy distribution in the 1-65 MeV range, similar to that produced by cosmic rays in the atmosphere found at flight altitudes and at sea level
For proton energies greater than 30 MeV, the distributions are somewhat flat, up to a sharp cutoff value close to the energy of the proton beam. This feature will be exploited to give NEPIR-0 pseudo-QMN capabilities: by irradiating a sample with neutrons produced using proton beams with two different energies, one can calculate, by subtraction of the renormalized distributions, the effects due to neutrons in the energy interval defined by the two cut-off values
Summary
NEPIR (NEutron and Proton IRradiation facility) is a multidisciplinary project at the new 30-70 MeV cyclotron of SPES [1] at the INFN National Laboratories of Legnaro (LNL). NEPIR will be used to study shielding against fast neutrons and protons For this purpose, the facility has been partially funded by the MIUR within the SPARE (Space Radiation Shielding) project: a joint INFN, ASI and Centro Fermi collaboration that deals with health risks due to cosmic radiation: a major showstopper for safe space exploration and colonization, where shielding techniques are the only practical countermeasure against radiation. The main goal of the SPARE project is to perform experimental tests, with neutrons and protons, of physical (active and passive shielding materials) and biomedical (hibernation) countermeasures for human space exploration. The SPARE project includes a test campaign of active and passive shielding materials for fast neutrons at LNL and for protons at the accelerator facility of TIFPA [8]. With the limited SPARE funds, we are building NEPIR-0: a simplified phase-0 fast neutron irradiation facility, adequate for the SPARE project, but still attractive for academic and electronics industrial users.
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