Positron Source from Betatron X-Rays Emitted in a Plasma Wiggler

• Published in: Proceedings of the 2005 Particle Accelerator Conference pp. 1625 - 1627
• Main Authors: Johnson, D.K., Clayton, C.E., Huang, C., Joshi, C., Lu, W., Marsh, K.A., Mori, W., Zhou, M., Barnes, C.D., Decker, F.J., Hogan, M.J., Iverson, R., Krejcik, P., O'Connell, C., Siemann, R., Walz, D.R., Deng, S., Katsouleas, T., Muggli, P., Oz, E.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 2005
• Subjects: Electron beams; Life estimation; Linear accelerators; Plasma accelerators; Plasma density; Plasma sources; Plasma x-ray sources; Positrons; Thermal stresses; Undulators
• ISBN: 9780780388598; 0780388593
• ISSN: 1944-4680; 2152-9582
• DOI: 10.1109/PAC.2005.1590857

In the E-167 plasma wakefield accelerator (PWFA) experiments in the Final Focus Test Beam (FFTB) at the Stanford Linear Accelerator Center (SLAC), an ultra-short, 28.5 GeV electron beam field ionizes a neutral column of Lithium vapor. In the underdense regime, all plasma electrons are expelled creating an ion column. The beam electrons undergo multiple betatron oscillations leading to a large flux of broadband synchrotron radiation. With a plasma density of 3 × 10 17 cm -3 , the effective focusing gradient is near 9 MT/m with critical photon energies exceeding 50 MeV for on-axis radiation. A positron source is the initial application being explored for these X-rays, as photo-production of positrons eliminates many of the thermal stress and shock wave issues associated with traditional Bremsstrahlung sources. Photo-production of positrons has been well-studied; however, the brightness of plasma X-ray sources provides certain advantages. In this paper, we present results of the simulated radiation spectra for the E-167 experiments, and compute the expected positron yield.