Hot electron production using the Texas Petawatt Laser irradiating thick gold targets

Abstract

We present data for relativistic hot electron production by the Texas Petawatt Laser irradiating solid Au targets with thickness between 1 and 4 mm. The experiment was performed at the short focus target chamber TC1 in July 2011, with intensities on the order of several x10 19 W.cm -2 and laser energies around 50 J. We discuss the design of an electron-positron magnetic spectrometer to record the lepton energy spectra ejected from the Au targets and present a deconvolution algorithm to extract the lepton energy spectra. We measured hot electron spectra out to ~ 50 MeV, which show a narrow peak around 10 -20 MeV, plus high energy exponential tail. The hot electron spectral shapes appear significantly different from those reported for other PW lasers. We did not observe direct evidence of positron production above the background.

Plasma scale-length effects on electron energy spectra in high-irradiance laser plasmas

“…The spatial resolution is generally 25-50 μm. Previous experiments show that image plates accurately measure the total electron energy impinging on the plates [25][26][27][28]. Figure 8 shows the unprocessed signal of the electron energy spectra obtained during the experiment.…”

Ultra-intense gamma-rays created using the Texas Petawatt Laser

“…The resulting point-spread function (psf) can be inverted to obtain the original gamma ray distribution given the distribution of Compton and pair-produced electrons. While this specific simulation was not directly validated, similar simulations have been validated for the production of gamma rays (see section III above), as well as positrons and electrons under different conditions [23,24]. Figure 8 shows the results of an end-to-end simulation, from photon incidence to the electron registering on the image plate.…”

“…Next, we constructed a detector response matrix (DRM) of the gamma-ray-to-Compton-electron process and used a previously developed psf [23] for the electron-to-image-plate signal to deconvolve the image plate results into a gamma-ray spectrum. These psfs were constructed by simulating a large number (10 3 ) of particles injected at fixed energies in 0.5 MeV intervals and using Matlab to obtain a pseudo-inverse of the resulting matrix.…”

Permanent‐magnet energy spectrometer for electron beams from radiotherapy accelerators

“…However, the system of Deasy et al also was designed to utilize radiographic film, making its design similar in principle to the methodology utilized in the present study. 13 The aim of the present study was to demonstrate how lightweight, permanent magnet spectrometers, previously used for studying electron and positron emission from laser pulses interacting with plasmas, 15,16 can be used for measuring the electron energy spectra of radiotherapy accelerators. This study used such a permanent magnet spectrometer originally developed by scientists at Rice University.…”

“…This study used such a permanent magnet spectrometer originally developed by scientists at Rice University. 16 Specifically, we determined a theoretical expression for the detector's dose response function and an analytical method for extracting the energy spectra from dose profiles that were measured using computed radiography (CR) strips placed downstream of a collimating system. Application of these techniques was demonstrated with measured electron beam data from an Elekta radiotherapy accelerator.…”