Speaker
Gerardo Claps
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.2039.pdf
Timepix chip interface detectors for X-rays, gammas and electrons monitor
on Laser Produced Plasmas
G. Claps1,2, D. Pacella1, F. Cordella1, F. Murtas2, D. Batani3, L. Volpe4, G. Gatti4
1
ENEA Fusion and Nuclear Safety Department, Via E. Fermi 45, 00044, Frascati, Italy
2
INFN – Laboratori Nazionali di Frascati, Via Enrico Fermi 40, 00044 Frascati, Italy
3
CELIA, Université Bordeaux 1, 351, Cours de la Liberation, 33405 Talence, France
4
CLPU, P. Científico, Calle del Adaja, 8, 37185 Villamayor de la Armunia, Salamanca, Spain
The physics of Laser Produced Plamas (LPPs) needs some particular diagnostic requirements.
In particular the X monitor of the plasma is difficult because typically X-ray emission is
concentrated in burst from few tens of ps to few ns, according to the power and pulse time width
of the laser. Then a measurement of photon flux is unfeasible. For the X-ray monitor we
realized the GEMpix [1], a proportional gas detector based on 3 consecutive Gas Electron
Multiplier (GEM) with a front-end electronic based on four Timepix [2] chips, with 512 x 512
squared pixels, 55 micron wide. It can work in a range of X-ray fluence of 6 orders of
magnitude. For LPPs, we exploit its ability to work Time over Threshold (ToT) mode: each
pixel registers digital counts proportional to the total charge released in the gas. Charge can be
amplified from the GEMs with a gain which can change on 4 order of magnitude, and then with
a big dynamic range. However, Spatial resolution depends on the intrinsic gain, ranging from
one to tens of pixels. In this work, we will present some results obtained on the Eclipse laser
facility (CELIA, Bordeaux, France) [3]. Together with X-rays, other particles can be produced
from LLPs, especially high energy gamma photons and electrons. In this case we characterized
the new Timepix3 [4] chip, based on silicon. It is a single chip of 256 x 256 pixels with a
bump-bonded 300 um thick silicon layer. Interaction of gammas with detector releases some
characteristic tracks due mainly to the Compton scattered electron. Similar tracks are released
by electrons. For each track we defined some parameters: cluster size, total charge (ToT mode),
roundness, linearity and so on. Based on these parameters we characterized the response of the
detector using some gamma and electron sources, in order to discriminate different energies. In
this manner, we defined some energy bands for gamma and electron particles. Then this
detector has been applied on VEGA laser facility (Salamanca, Spain) to characterize in energy
of the gammas coming from laser plasma interaction. The use of a 2D detector allowed to
separate the tracks, then, based on the source detector calibration and defining the track
parameters, we distinguished in energy the gamma photons.
[1] F. Murtas, 3rd International conference on micropattern gaseous detectors, 1–6july, 2013, Zaragoza, Spain
[2] X. Llopart et al., Nucl. Instr. and Meth. A 581 (2007) 485.
[3] G. Claps et al., The GEMpix detector as new soft X-rays diagnostic tool for laser produced plasmas (2016)
Review of Scientific Instruments, 87 (10), art. no. 103505
[4] T. Poikela et al., Timepix3: a 65K channel hybrid pixel readout chip with simultaneous ToA/ToT and sparse
readout, 15th international workshop on radiation imaging detectors 23–27 June 2013, Paris, France
