A spectrometer for ultrashort gamma-ray pulses with photon energies greater than 10 MeV

Abstract

We present a design for a pixelated scintillator based gamma-ray spectrometer for non-linear inverse Compton scattering experiments. By colliding a laser wakefield accelerated electron beam with a tightly focused, intense laser pulse, gamma-ray photons up to 100 MeV energies and with few femtosecond duration may be produced. To measure the energy spectrum and angular distribution, a 33 × 47 array of cesium-iodide crystals was oriented such that the 47 crystal length axis was parallel to the gamma-ray beam and the 33 crystal length axis oriented in the vertical direction. Using an iterative deconvolution method similar to the YOGI code, modeling of the scintillator response using GEANT4 and fitting to a quantum Monte-Carlo calculated photon spectrum, we are able to extract the gamma ray spectra generated by the inverse Compton interaction.

Compact spectroscopy of keV to MeV X-rays from a laser wakefield accelerator

“…These algorithms can easily be transferred to manycore processors since each unfolding is performed 100 times and each run is independent. These computations can be parallelized to reduce the unfolding time by a factor of 100 or more to ms. To achieve data acquisition rates commensurate with such computational speed, image plates will need to be replaced with prompt scintillators compatible with 10 Hz LWFA repetition rates 63 , 64 . In this geometry, plastic scintillators or scintillating fiber arrays alternate with absorbing material and the side of the stack is imaged with a camera or can be connected directly to photomultiplier tubes (PMTs) 65 .…”

Development of control mechanisms for a laser wakefield accelerator-driven bremsstrahlung x-ray source for advanced radiographic imaging

“…In our study, a differential self-filtering diagnostic was utilised, in order to retain sub-centimetre spatial resolution while obtaining some spectral information with a repetition rate higher than our laser shot rate (0.05 Hz). The specific detector had been fielded elsewhere [32,33], demonstrating its suitability in the relevant energy range. The X-ray beam was incident on a 47× 33 array of scintillating caesium iodide (CsI) crystals, each 5 mm × 5 mm × 50 mm in the geometry shown in Figure 2.…”

“…In extracting the photon spectrum, this detector has a non-uniqueness problem which must be overcome. To solve this issue, the spectrum is assumed to be of the form [32,33]:…”

Toward the observation of interference effects in nonlinear Compton scattering

“…(Measurement of such photon energies may be performed e.g. by using a pixelated scintillator [40].) We see, in general, that the position of maxima and minima can change position when interference is taken into account: instead of two symmetric off-centre maxima when interference is neglected in (a) we see three maxima when interference is included at the centre of image (b) [7]; in the middle panels with δs = 0.02 at larger s c = 0.15, interference splits the single central broad maximum (c) into a sharp ring structure with a central minimum in (d).…”