Thursday, January 21, 2020 at 4:00 pm

Speaker: Ralitsa Sharankova, Tufts University

Title:The MicroBooNE experiment and applications of Machine Learning and Deep Learning

Abstract:

MicroBooNE is a short baseline neutrino experiment situated at Fermilab. It measures neutrinos from the Booster Neutrino Beam (BNB) with a 85t Liquid Argon Time Projection Chamber (LArTPC) detector. The main scientific goals of MicroBooNE are to explore the low energy electron neutrino spectrum and to measure neutrino-LAr interaction cross-sections. Measuring low energy electron neutrinos is aimed at probing the excess of neutrino-like events observed by the MiniBooNE experiment in the [200,600] MeV region, which may hint at BSM physics. Neutrino cross section measurements on LAr are an important input for the DUNE/LBNF program. Several low-energy excess analyses are taking place in parallel in MicroBooNE, using independent event reconstruction techniques and different signal topologies. The Deep Learning (DL) group employs machine learning techniques to extract information used in event reconstruction. In this talk I will briefly present the status of the DL low-energy excess analysis, then introduce several applications of machine learning and deep learning to LArTPC images. I will conclude with some ideas on future application of ML/DL to accelerator operations.

Tuesday, February 9, 2020 at 4:00 pm

Speaker: Elias Metral, CERN

Title:Intrabunch motion

Abstract:

Until now, the intrabunch signals superimposed turn after turn, as observed from a pickup monitor in the presence of coherent beam instabilities, have only been explained theoretically for independent longitudinal or transverse beam oscillation modes, i.e., when the bunch intensity is sufficiently low compared to the mode coupling threshold. These signals exhibit clear head/tail symmetries and they are called standing-wave patterns. However, many pictures measured in particle accelerators or simulated with macroparticle tracking codes exhibit clear head/tail asymmetries. How can this be understood theoretically? The purpose of this seminar (based on the recently published PRAB paper https://journals.aps.org/prab/pdf/10.1103/PhysRevAccelBeams.24.014401) is to answer to this question for the case of impedance-driven instabilities, discussing also the influence of space charge, electron cloud and beam-beam. Better characterizing an instability is the first step before trying to find appropriate mitigation measures and push the performance of a particle accelerator. The evolution of the intrabunch motion with intensity is a fundamental observable with high-intensity high-brightness beams.

Tuesday, March 2, 2020 at 4:00 pm

Speaker: Kiersten Ruisard, ORNL

Title:High range and high dimensions: Understanding the beam distribution at the SNS Beam Test Facility

Abstract:

Mitigation of beam loss is an ever-present concern in high-power accelerators. To date, loss predictions from PIC simulation have not been shown to reproduce control room measurements. This seminar will discuss on-going work at the SNS Beam Test Facility (BTF) to investigate this model/measurement discrepancy, with the goal of demonstrating loss-accurate modeling. We expect a significant improvement can be gained through more complete knowledge of the bunch distribution. In particular, the exact form of the 6D phase space distribution will influence beam evolution. The BTF project combines full-and-direct 6D measurement of the bunch distribution downstream of the RFQ and high dynamic range measurement of the evolved bunch. This talk will describe measurement capabilities at the BTF as well as report recent progress in understanding the beam distribution and accelerator model.

Tuesday, April 6, 2020 at 4:00 pm

Speaker: Georg Hoffstaetter, Cornell

Title:The Cornell-BNL ERL Test Accelerator (CBETA), an energy-saving accelerator

Abstract:

As accelerators become larger and their beams require more power, efficiency becomes an important paradigm. Energy Recovery Linacs (ERLs), the use of superconducting cavities (SRF), and permanent magnets address this concern. A collaboration between Cornell University and Brookhaven National Laboratory has designed, constructed, and commissioned CBETA, the Cornell-BNL ERL Test Accelerator at Cornell University, culminating in the first 4-turn operation that recovers energy into SRF cavities. Energy Recovery Linacs decelerate a used beam to capture its energy and use it for the acceleration of new beam. CBETA is the first SRF ERL with multiple acceleration and deceleration turns. Another first is the larger energy-acceptance return loop that simultaneously transports 7 beams of different energy through a Fixed Field Alternating-gradient (FFA) lattice that is comprised of permanent magnets. Successfully establishing 4-turn energy recovery at CBETA is especially relevant in the light of the increasing importance that ERLs have obtained: ERLs are part of the hadron coolers for the EIC, they are part of the LHeC plans, they are an integral component of an FCC-ee design option, they can be drivers for low energy nuclear physics experiments, and they have been investigated as drivers for compact Compton-x-ray sources and for industrial lithography.

Tuesday, April 13, 2020 at 2:00 pm

Speaker: Alexey Burov, FNAL

Title:Longitudinal Modes of Bunched Beams with Weak Space Charge

Abstract:

Longitudinal collective modes of a bunched beam with a repulsive inductive impedance (the space charge below transition or the chamber inductance above it) are analytically described by means of reduction of the linearized Vlasov equation to a parameter-less integral equation. For any multipolarity, the discrete part of the spectrum is found to consist of infinite number of modes with real tunes, which limit point is the incoherent zero-amplitude frequency. In other words, notwithstanding the RF bucket nonlinearity and potential well distortion, the Landau damping is lost. Hence, even a tiny coupled-bunch interaction makes the beam unstable; such growth rates for all the modes are analytically obtained for arbitrary multipolarity. In practice, however, the finite threshold of this loss of Landau damping is set either by the high-frequency impedance roll-off or intrabeam scattering. Above the threshold, growth of the leading collective mode should result in persistent nonlinear oscillations.

Tuesday, April 20, 2020 at 4:00 pm

Speaker: Mohammad Eshraqi, ESS

Title:The ESS Linear Accelerator

Abstract:

The European Spallation Source (ESS), currently under construction in Lund, Sweden, is the world’s most powerful linear accelerator driving a neutron spallation source, with an average power of 5 MW at 2.0 GeV. The linac accelerates a proton beam of 62.5 mA peak current at 4 % duty cycle (2.86 ms at 14 Hz). The accelerator uses a normal conducting front-end bringing the beam energy to 90 MeV, beyond that the acceleration up to 2 GeV is performed using superconducting structures. This talk will give an overview of the status of the ESS accelerator and the upcoming beam commissioning through the RFQ.