The Soreq Applied Research Accelerator Facility (SARAF) - Overview, Research Programs and Future Plans

The Soreq Applied Research Accelerator Facility (SARAF) is under construction in the Soreq Nuclear Research Center at Yavne, Israel. When completed at the beginning of the next decade, SARAF will be a user facility for basic and applied nuclear physics, based on a 40 MeV, 5 mA CW proton/deuteron superconducting linear accelerator. Phase I of SARAF (SARAF-I, 4 MeV, 2 mA CW protons, 5 MeV 1 mA CW deuterons) is already in operation, generating scientific results in several fields of interest. The main ongoing program at SARAF-I is the production of 30 keV neutrons and measurement of Maxwellian Averaged Cross Sections (MACS), important for the astrophysical s-process. The world leading Maxwellian epithermal neutron yield at SARAF-I ($5\times 10^{10}$ epithermal neutrons/sec), generated by a novel Liquid-Lithium Target (LiLiT), enables improved precision of known MACSs, and new measurements of low-abundance and radioactive isotopes. Research plans for SARAF-II span several disciplines: Precision studies of beyond-Standard-Model effects by trapping light exotic radioisotopes, such as $^6$He, $^8$Li and $^{18,19,23}$Ne, in unprecedented amounts (including meaningful studies already at SARAF-I); extended nuclear astrophysics research with higher energy neutrons, including generation and studies of exotic neutron-rich isotopes relevant to the rapid (r-) process; nuclear structure of exotic isotopes; high energy neutron cross sections for basic nuclear physics and material science research, including neutron induced radiation damage; neutron based imaging and therapy; and novel radiopharmaceuticals development and production. In this paper we present a technical overview of SARAF-I and II, including a description of the accelerator and its irradiation targets; a survey of existing research programs at SARAF-I; and the research potential at the completed facility (SARAF-II).Comment: 32 pages, 31 figures, 10 tables, submitted as an invited review to European Physics Journal

Neutron spectrometry of a liquid Lithium based (p, n) beam at SARAF facility using the broad-energy range directional spectrometer CYSP

An intense neutron beam produced via 7 Li(p, n) 7 Be reaction on a newly developed high-power liquid Lithium target (LiLiT) is available at SARAF (Soreq Applied Research Accelerator Facility) facility, Israel. Its spectrum was determined using the CYSP (CYlindrical SPectrometer), a new directional neutron spectrometer which incorporates the functionality of the Bonner spheres in a single cylindrical moderator. The advantages of this spectrometer are that the neutron spectrum is derived in only one exposure, and that its directional response is not affected by room- and air-scattered neutrons. The data from the CYSP spectrometer were analysed using the FRUIT unfolding code

A 50 kW Liquid-Lithium Target for BNCT and Material-Science Applications

A compact Liquid Lithium Target (LiLiT) has been operating at SARAF for several years with beam power of several kW (1.9-2.5 MeV, up to 2 mA). When bombarding the lithium with low energy protons neutrons are generated. The neutron source, mainly used for nuclear astrophysics research, was decommissioned in 2016 towards an upgraded model - with possible applications to Boron Neutron Capture Therapy (BNCT) and material-science studies. The improved version has been designed to sustain 50 kW proton beam power (2.5 MeV, ~20 mA) to provide sufficient neutron flux required for clinical BNCT application. The new model has a 50 mm wide lithium jet to enable dissipation of the higher beam power and an improved heat exchanger to remove the power to a secondary cooling loop. A new Annular Linear INduction electro-magnetic pump (ALIN) has been designed and built to provide the required lithium flow rate. Other mechanical improvements facilitate the maintenance of the system and the robustness of operation. Radiological risks due to the 7Be produced in the reaction are reduced by using an integrated lead shielding of the lithium reservoir. An integrated neutron moderator is being designed to adjust the neutron energy to the spectrum best suited to BNCT. A low power (6 kW) model of the new design with a narrower nozzle (18 mm wide) and a rotating-magnet electro-magnetic pump is operating at SARAF to support the ongoing astrophysics and nuclear research program [1], [2]. To fulfill clinical BNCT, the upgraded LiLiT model will require an accelerator of appropriate energy and intensity. The design features of the new system are presented in this paper

A 50 kW Liquid-Lithium Target for BNCT and Material-Science Applications

A compact Liquid Lithium Target (LiLiT) has been operating at SARAF for several years with beam power of several kW (1.9-2.5 MeV, up to 2 mA). When bombarding the lithium with low energy protons neutrons are generated. The neutron source, mainly used for nuclear astrophysics research, was decommissioned in 2016 towards an upgraded model - with possible applications to Boron Neutron Capture Therapy (BNCT) and material-science studies. The improved version has been designed to sustain 50 kW proton beam power (2.5 MeV, ~20 mA) to provide sufficient neutron flux required for clinical BNCT application. The new model has a 50 mm wide lithium jet to enable dissipation of the higher beam power and an improved heat exchanger to remove the power to a secondary cooling loop. A new Annular Linear INduction electro-magnetic pump (ALIN) has been designed and built to provide the required lithium flow rate. Other mechanical improvements facilitate the maintenance of the system and the robustness of operation. Radiological risks due to the 7Be produced in the reaction are reduced by using an integrated lead shielding of the lithium reservoir. An integrated neutron moderator is being designed to adjust the neutron energy to the spectrum best suited to BNCT. A low power (6 kW) model of the new design with a narrower nozzle (18 mm wide) and a rotating-magnet electro-magnetic pump is operating at SARAF to support the ongoing astrophysics and nuclear research program [1], [2]. To fulfill clinical BNCT, the upgraded LiLiT model will require an accelerator of appropriate energy and intensity. The design features of the new system are presented in this paper

Reactions along the astrophysical s-process path and prospects for neutron radiotherapy with the Liquid-Lithium Target (LiLiT) at the Soreq Applied Research Accelerator Facility (SARAF)

Neutrons play a dominant role in the stellar nucleosynthesis of heavy elements and the quest for accurate experimental determinations of neutron-induced reaction cross sections becomes more stringent with the refinement of nuclear and astrophysical models. We review here an experimental nuclear-astrophysics program using a high-intensity neutron source based on the 7Li(p, n)7Be reaction with a Liquid-Lithium Target (LiLiT) at the Soreq Applied Research Accelerator Facility (SARAF) Phase I. The quasi-Maxwellian neutron spectrum with effective thermal energy $kT \approx 30$ keV, characteristic of the thick-target 7Li(p, n) yield at proton energy $E_p \approx 1.92$ MeV close to its neutron threshold, is well suited for laboratory measurements of neutron capture reactions along the astrophysical s -process path. The high-intensity proton beam (in the mA range) of SARAF and the high power (few kW) dissipation of LiLiT result in the most intense source of neutrons available today at stellar-like energies. The principle, design and properties of the LiLiT device and recent measurements of Maxwellian Averaged Cross Sections (MACS) based on activation of targets of astrophysical interest are described. Decay counting or atom counting methods (accelerator mass spectrometry, atom-trap trace analysis) are used for the detection of short-lived or long-lived activation products, respectively. In a different realm of applications, the 7Li(p, n) reaction is a leading candidate as an accelerator-based neutron source for Boron Neutron Capture Therapy (BNCT). The high neutron yield achievable from a liquid-lithium target, its sustainability of operation under kW-power incident beams and the recent availability of small-size high-intensity accelerators are compatible with a hospital-based clinical facility. An effort towards the characterization and realization of a liquid-lithium target for BNCT is reviewed. Perspectives of pending and future developments towards SARAF Phase II, based on a 40MeV, 5mA CW proton/deuteron superconducting linear accelerator, are summarized

Fast chopper for single radio-frequency quadrupole bunch selection for neutron time-of-flight capabilities

A fast chopper system has been developed and tested for single bunch selection with the radio-frequency quadrupole (RFQ) accelerating element of the Soreq Applied Research Accelerator Facility (SARAF). The fast chopper consists of a high voltage (HV) deflector just before the RFQ, providing both positive and negative HV deflections and fast HV switching between polarities to enable momentary transmission of a single prebunch to the RFQ. Presently, the system enables single bunch selection for protons and deuterons at a repetition rate as determined by the user of up to 200 kHz, with bunch transmission of up to 50%, and with neighboring bunch contamination of less than 15%. Single bunch selection provides SARAF with fast neutron time-of-flight (TOF) capabilities. Measurements performed with liquid scintillation detectors show clear gamma and neutrons peaks, with TOF resolution of about 1 nanosecond FWHM. Beam dynamics simulations suggest possibilities for further improvements of the fast chopper and single bunch selection characteristics, with a significant lowering or elimination of the neighboring bunches, enhanced TOF resolution, and increased repetition rate to above 200 kHz. Fast neutron TOF capabilities, especially at phase II of SARAF, will provide exceptional opportunities for neutron induced reaction measurements for nuclear technology and fundamental research

The Soreq Applied Research Accelerator Facility (SARAF): Overview, research programs and future plans

The Soreq Applied Research Accelerator Facility (SARAF) is under construction in the Soreq Nuclear Research Center at Yavne, Israel. When completed at the beginning of the next decade, SARAF will be a user facility for basic and applied nuclear physics, based on a 40 MeV, 5 mA CW proton/deuteron superconducting linear accelerator. Phase I of SARAF (SARAF-I, 4 MeV, 2 mA CW protons, 5 MeV 1 mA CW deuterons) is already in operation, generating scientific results in several fields of interest. The main ongoing program at SARAF-I is the production of 30 keV neutrons and measurement of Maxwellian Averaged Cross Sections (MACS), important for the astrophysical s-process. The world leading Maxwellian epithermal neutron yield at SARAF-I ($5\times 10^{10}$ epithermal neutrons/sec), generated by a novel Liquid-Lithium Target (LiLiT), enables improved precision of known MACSs, and new measurements of low-abundance and radioactive isotopes. Research plans for SARAF-II span several disciplines: Precision studies of beyond-Standard-Model effects by trapping light exotic radioisotopes, such as $^6$He, $^8$Li and $^{18,19,23}$Ne, in unprecedented amounts (including meaningful studies already at SARAF-I); extended nuclear astrophysics research with higher energy neutrons, including generation and studies of exotic neutron-rich isotopes relevant to the rapid (r-) process; nuclear structure of exotic isotopes; high energy neutron cross sections for basic nuclear physics and material science research, including neutron induced radiation damage; neutron based imaging and therapy; and novel radiopharmaceuticals development and production. In this paper we present a technical overview of SARAF-I and II, including a description of the accelerator and its irradiation targets; a survey of existing research programs at SARAF-I; and the research potential at the completed facility (SARAF-II).Comment: 32 pages, 31 figures, 10 tables, submitted as an invited review to European Physics Journal