Bulletin of the American Physical Society
2020 Fall Meeting of the APS Division of Nuclear Physics
Volume 65, Number 12
Thursday–Sunday, October 29–November 1 2020; Time Zone: Central Time, USA
Session LA: Compact accelerator systems for nuclear physics |
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Chair: Paul Gueye, MSU-NSCL/FRIB |
Saturday, October 31, 2020 10:30AM - 11:06AM |
LA.00001: Highly spin polarized electron and positron beams at a compact accelerator facility Invited Speaker: Joseph Grames Over the past 30 years polarized electron and positron beams with rather high energies (above 1 GeV) have been demonstrated at large scale particle accelerators world-wide. Proposed future linear colliders aim for even higher energies, colliding beams of polarized electrons and positrons above 100 GeV. However, highly polarized electron and positron beams are not limited to only the large scale facilities, but are equally accessible to the compact accelerator facility operating at the MeV energy scale. Notably, the workhorse method for providing polarized electron beams, via photoemission from GaAs semi-conductors, occurs within a high voltage photo-gun which operates at relatively low accelerating voltage (less than 200 kV) and is often connected to an adjacent low-energy beamline composed of spin rotators to set the polarized beam direction, well suited to a compact footprint. Additionally, polarized electron beams accelerated to MeV energy have been demonstrated to be an efficient method to produce highly spin polarized positrons, via the electro-magnetic shower of the polarized electron beam when interacting with a suitably high-Z target. In this presentation I will review the progress and present-day capability and technology of polarized GaAs photo-guns and discuss the development of an MeV energy polarized positron beam source at Jefferson Lab. Examples of interesting physics experiments using polarized electron and positron beams at compact accelerator facilities will be highlighted. [Preview Abstract] |
Saturday, October 31, 2020 11:06AM - 11:42AM |
LA.00002: Compact Superconducting RF Electron Accelerating Systems Invited Speaker: Matthias Liepe Superconducting RF (SRF) technology is at the threshold of a radical change enabled by recent progress in the performance of Nb$_{\mathrm{3}}$Sn SRF cavities. Next-generation Nb$_{\mathrm{3}}$Sn cavities will enable a new class of simple, robust, power efficient, and compact accelerating sections with turn-key style operation. Higher temperature operation of Nb$_{\mathrm{3}}$Sn cavities avoids the complexity and cost of superfluid cryogenic LHe refrigerators and significantly reduces energy consumption of the cryogenic cooling plant. For compact accelerators, Nb$_{\mathrm{3}}$Sn based SRF modules can even be operated cryogen-free via conduction cooling by cryocoolers, thereby greatly simplifying the complexity of SRF technology. These changes will make powerful SRF technology accessible to a wide range of future applications, including compact nuclear physics accelerators. In this talk, I will give an overview of these exciting Nb$_{\mathrm{3}}$Sn SRF developments at Cornell University, the Center for Bright Beams, and elsewhere, and will discuss state-of-the-art performance. [Preview Abstract] |
Saturday, October 31, 2020 11:42AM - 12:18PM |
LA.00003: All-laser driven MeV photon source for photonuclear applications Invited Speaker: Sudeep Banerjee I will discuss the development of a tunable, MeV photon source based on all-optical inverse Compton scattering. In this device, high-energy electron beams are generated by the process of laser-wakefield acceleration in which a high-intensity laser pulse interacts with a supersonic gas jet and drives relativistic plasma waves. The laser generated electron beam then interacts with a second laser pulse in a nearly counterpropagating geometry to produce high-energy photons by the process of inverse Compton scattering. By tuning the energy of the laser-driven electron accelerator and using both the fundamental and second harmonic of a Titanium:Sapphire laser (800 nm) we have demonstrated the generation of high-brightness x-ray beams spanning the spectral range of 50 keV -- 20 MeV. These x-rays are characterized by a variety of methods. The spatial profile of the collimated x-rays is determined using pixelated CsI detectors while the spectral content is determined using techniques such as single photon spectroscopy, attenuation measurements and the ability to trigger photonuclear reactions. The ability to use this source in the energy range \textless 1 MeV makes it uniquely suited for isomeric studies. We have applied the source to excite isomeric transitions in Indium and Holmium including measurement of decay lifetimes. This novel table-top source has been used for high-energy radiography and the identification of actinides in shielded configuration. [Preview Abstract] |
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