DOE EPSCoR Proposal

Abstract

We propose to develop a partnership between Jefferson Lab's (JLab) Continuous Electron Beam Accelerator Facility (CEBAF) in Newport News, VA and the Idaho Accelerator Center (IAC) at Idaho State University. The partnership will initially be nurtured through a research and development project designed to construct a positron source for the CEBAF. The first year of this proposal will be used to benchmark the predictions of our current simulation with positron production efficiency measurements at the IAC. The second year will use the benchmarked simulation to design a beamline configuration which optimizes positron production efficiency while minimizing radioactive waste. The second year will also be devoted to the design and construction of a positron converter capable of sustaining the heat load from high luminosity positron production. The final year will be used to quantify the performance of the positron source and measure the source's radiation footprint. A joint research and development project to construct a positron source for use by the CEBAF will bring together the experiences of both electron accelerator facilities and solidify this partnership for future projects. Our intention is use the project as a spring board towards developing a program of accelerator based research and education which will train students to meet the needs of both facilities as well as provide a pool of trained scientists for others.

Project Objectives

We propose to develop a partnership between Jefferson Lab's (JLab) Continuous Electron Beam Accelerator Facility (CEBAF) in Newport News, VA and the Idaho Accelerator Center (IAC) at Idaho State University. The partnership will initially be nurtured through a research and development project designed to construct a positron source for the CEBAF. The first year of this proposal will be used to benchmark the predictions of our current simulation~\cite{HuntPos} with positron production efficiency measurements at the IAC. The second year will use the benchmarked simulation to design a beamline configuration which optimizes positron production efficiency. The second year will also be devoted to designing a positron converter capable of sustaining the heat load from high positron luminosity production. The final year will be used to measure the capabilities of the positron source and the source's radiation footprint. A joint research and development project to construct a positron source for use by the CEBAF will bring together the experiences of both electron accelerator facilities and solidify this partnership for future projects.

One of the more common methods used to create positrons is to bombard a target of high atomic number (Z), typically Tungsten, with electrons of sufficient energy to generate a shower of secondary electrons, photons, and positrons. Electron accelerators have used this technique to produce positron beams with intensities approaching $10^7$e$^+$/sec~\cite{Ito_1991} at 100 MeV energies that are at least an order of magnitude larger than traditional radioactive source based beams~\cite{Radbeam}. Positron beams have also been produced at GeV beam energies with intensities of $10^{10}$e$^+$/sec %~\cite{ILC} for use by the high energy physics community. The current conceptual design of a positron source for use at the CEBAF would rely on the production of positrons at relatively lower energies (MeV). Positrons would be produced using electrons from the current source which have been accelerated to energies between 10 and 20 MeV. Although these low energies produce less intense positron beams our current simulation predicts that we will be able to produce positron currents beyond a nanoamp which are sufficient for our needs. This energy selection has the feature of being close to the 10 MeV neutron production threshold~\cite{n_threshold} allowing us to reduce radioactive waste.

Year 1

1. Install positron beam line.
2. Check positron productions efficiency simulations for 10-20 MeV electrons on Tungsten Target (expecing 17 nA of positrons for a 10mA electron beam at E=?)
3. Investigate differences between simulation and data, most likely need another week of beam to change configuration

Year 2

1. Measure production efficiency for different Tungsten converter target thicknesses (100 microns -> 1mm in 100 micron steps)
2. Measure positron emmitance and compare to simulation predictions
3. Measure brightness as a function of quad setting (quads change emmitance)
4. measure positron output as a function of beam current
5. Begin designing tungsten converter capable of handling high heat load
6. CEBAF can accept particles into acceleration stage as long as [math]\frac{\Delta E}{E} \leq 10^{-3}[/math]
7. Electrons are injected at 500 MeV (1 GeV) for a 6 GeV (12 GeV) CEBAF. Currently [math]\frac{\Delta E}{E} \leq 10^{-5}[/math]

Year 3

1. Conceptual Positron source design level 1 (CD1)
2. IAC beam is x 40 less power than what will be needed at JLAB

Parts list

1. Media:FaradayCup.pdfFC $5k 400 W max power
2. Media:ConverterMotor.pdf

Latex File

The LaTex file for this proposal is under Media:Positrons.txt