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Start of funding 01.07.2017
High-Capacity Positron Accumulator with High Energy Resolution Beam Capabilities on NEPOMUC
Dr. Christoph Hugenschmidt
Technische Universität München
FRM-II
Prof. Dr. Clifford M. Surko
University of California, San Diego
Department of Physics
Positrons (i.e., the antiparticles of electrons) are extremely useful for a range of scientific and technological
applications. NEPOMUC (NEutron induced POsitron source MUniCh) at the FRMII research reactor
provides one of the most intense positron beams worldwide. Under the guidance of Dr. Christoph
Hugenschmidt and his research group at TUM, it has proven useful for fundamental physics studies and
state-of-the-art experiments to characterize materials. Professor Cliff Surko and his research group at
UCSD have pioneered the development of new plasma-based methods to accumulate, store and deliver
large bursts of positrons and to form tunable, high-energy-resolution positron beams. Combining these
technologies has considerable potential for furthering basic science and forefront technologies. Within
this project we aim to implement a state-of-the-art positron accumulator at NEPOMUC. In near term,
this device should be able to deliver bursts in excess of 108 positrons in as short a time as 10 ns.
Final report:
The aim of the cooperation between the TUM, the UCSD and the IPP is to implement a new type of positron accumulator at the strongest source of low-energy positrons NEPOMUC at FRM II. It is planned to use the BGT to generate high-intensity 10ns short positron pulses with 108 positrons for the first time and to make them available for basic experiments and surface studies.
As part of the BaCaTeC funding, Prof. Cliff Surko was invited to a workshop in which the expertise of the different groups came together. The aspects of plasma physics, cooling and accumulation of charged particles as well as physics with low-energy positrons were discussed in order to define the technical boundary conditions of a positron accumulator at the NEPOMUC Beamline.
The most important goal of defining all technical design parameters of the entire “Positron Buffer Gas Trap (BGT)” system was successfully achieved. Basically, the BGT consists of external magnetic field coils and a series of electrodes that are designed in such a way that positrons can be transported without loss in the beamline via differential pumping, and positrons can be specifically cooled in areas of increased nitrogen pressure to be subsequently collected in a particle trap. Additional third-party funding could already be obtained for the project in advance of the BaCaTeC funding, so that the BGT can be installed in the positron beamline at NEPOMUC in 2020.