HARPO - TPC for High Energy Astrophysics and Polarimetry from the MeV to the TeV

Gros, Philippe

doi:10.22323/1.213.0133

Cited by 8 publications

(7 citation statements)

References 15 publications

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“…The HARPO (Hermetic ARgon POlarimeter) detector [7] is a demonstrator of the performance of a TPC for measuring polarised γ rays. It was designed for a validation on the ground in a photon beam.…”

Section: Methodsmentioning

confidence: 99%

Performance measurement of HARPO: A time projection chamber as a gamma-ray telescope and polarimeter

Gros

Amano

Attié

et al. 2018

Astroparticle Physics

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We analyse the performance of a gas time projection chamber (TPC) as a high-performance gamma-ray telescope and polarimeter in the e + e − pair-creation regime. We use data collected at a gammaray beam of known polarisation. The TPC provides two orthogonal * philippe.gros at in2p3.fr projections (x, z) and (y, z) of the tracks induced by each conversion in the gas volume. We use a simple vertex finder in which vertices and pseudo-tracks exiting from them are identified.We study the various contributions to the single-photon angular resolution using Monte Carlo simulations, compare them with the experimental data and find that they are in excellent agreement. The distribution of the azimuthal angle of pair conversions shows a bias due to the non-cylindrical-symmetric structure of the detector. This bias would average out for a long duration exposure on a space mission, but for this pencil-beam characterisation we have ensured its accurate simulation by a double systematics-control scheme, data taking with the detector rotated at several angles with respect to the beam polarisation direction and systematics control with a non-polarised beam.We measure, for the first time, the polarisation asymmetry of a linearly polarised gamma-ray beam in the low energy pair-creation regime. This sub-GeV energy range is critical for cosmic sources as their spectra are power laws which fall quickly as a function of increasing energy.This work could pave the way to extending polarised gamma-ray astronomy beyond the MeV energy regime.

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Section: Methodsmentioning

confidence: 99%

Performance measurement of HARPO: A time projection chamber as a gamma-ray telescope and polarimeter

Gros

Amano

Attié

et al. 2018

Astroparticle Physics

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“…The HARPO Collaboration built a high-pressure (0.5 -5 bar) gas TPC prototype [14] that uses an hybrid GEM-micromegas amplification system that we characterised precisely [28]. The anode plane is segmented into 2 orthogonal series (x, y) of strips, rather than into pads, so as to limit the number of electronic channels and therefore the power consumption, a key factor for a detector intended to fly a space mission.…”

Section: Harpo: the Experimentsmentioning

confidence: 99%

HARPO, a gas TPC active target for high-performance γ-ray astronomy; demonstration of the polarimetry of MeV γ-rays converting to
Bernard
¹

2019
Nuclear Instruments and Methods in Physics Research Section A:
10
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4
0
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No γ-ray polarimeter sensitive above 1 MeV has ever flown space. γ-ray polarimetry would be a new window on the radiative processes at work in cosmic sources, processes that produce linearly polarised emission, each of which with different polarisation fractions. The HARPO Collaboration has designed, built and characterised on beam a gas-TPC active target with which we have demonstrated for the first time the polarimetry of a linearly polarised MeV γ-ray beam, from the analysis of the conversions to e + e − pairs.

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“…The TPC was filled with a mixture of 5% of iC 4 H 10 in argon and was operated at 220 V/cm of electric field to drift the primary electrons to the readout plane composed by two GEM foils [4] and a bulk Micromegas [5,6] on top of the strips. The detector, the electronic chain and its innovative trigger system called FAST (Fully Automated Switched Trigger) have been described in details in [7,8,9].…”

Section: Prototype Desciption and New Subaru Photon Beam Campaignmentioning

confidence: 99%

HARPO, prototype of a gamma-ray polarimeter: Results of a polarised photon beam test between 1.7 and 74 MeV

Attié¹,

Amano²,

Baron³

et al. 2017

Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017)

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Access to the photon polarisation in the 1-100 MeV energy range is a challenge for the next generation of space telescopes. The current telescopes in space are almost blind in this energy range, mainly due to the degradation of the angular resolution of e+e-pair and due to elastic scattering in the matter. Pair-conversion detector technologies as gaseous detectors are a promising alternative to the technologies based on tungsten-converter/thin-sensitive-layer stacks such as COS-B/EGRET/Fermi-LAT, firstly to improve the single-photon angular resolution and secondly for the polarisation information. The use of a time projection chamber (TPC) as a target and a tracking detector will improve by up to one order of magnitude the single-photon angular resolution (0.5 • @100 MeV) with respect to the Fermi-LAT (5 • @100 MeV), and by up to a factor of three with respect to what can be expected for silicon detectors (1.0-1.5 • @100 MeV). With such a good angular resolution, a TPC can close the sensitivity gap at the level of 10 −6 MeV/cm 2 .s) between 3 and 300 MeV despite having e lower sensitive mass. Furthermore, this good single-track angular resolution allows us to measure the linear polarisation fraction. The HARPO (Hermetic ARgon POlarimeter) detector prototype that we built is a high pressure (0.5-4 bar) low pile-up and low-diffusion gas detector. We will present the results of its highstatistics characterisation in the 1.7-74 MeV fully-polarised and non-polarised gamma-ray beam provided by the BL01 line at NewSUBARU. The excellent value of the polarisation asymmetry dilution factor that we measured opens the possibility of having a polarimeter in space working in the MeV-GeV energy range. In conclusion, we will present the design of a balloon-flight prototype ST3G (Self-Triggered Time projection chamber as a Gamma-ray Telescope) which is being developed. We will discuss its expected performance.

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HARPO - TPC for High Energy Astrophysics and Polarimetry from the MeV to the TeV

Cited by 8 publications

References 15 publications

Performance measurement of HARPO: A time projection chamber as a gamma-ray telescope and polarimeter

Performance measurement of HARPO: A time projection chamber as a gamma-ray telescope and polarimeter

HARPO, a gas TPC active target for high-performance γ-ray astronomy; demonstration of the polarimetry of MeV γ-rays converting to
Bernard
¹

2019
Nuclear Instruments and Methods in Physics Research Section A:
10
0
4
0
View full text Add to dashboard Cite

HARPO, prototype of a gamma-ray polarimeter: Results of a polarised photon beam test between 1.7 and 74 MeV

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HARPO - TPC for High Energy Astrophysics and Polarimetry from the MeV to the TeV

Cited by 8 publications

References 15 publications

Performance measurement of HARPO: A time projection chamber as a gamma-ray telescope and polarimeter

Performance measurement of HARPO: A time projection chamber as a gamma-ray telescope and polarimeter

HARPO, a gas TPC active target for high-performance γ-ray astronomy; demonstration of the polarimetry of MeV γ-rays converting to Bernard1 2019Nuclear Instruments and Methods in Physics Research Section A: 10040View full textAdd to dashboardCite

HARPO, prototype of a gamma-ray polarimeter: Results of a polarised photon beam test between 1.7 and 74 MeV

Contact Info

Product

Resources

About

HARPO, a gas TPC active target for high-performance γ-ray astronomy; demonstration of the polarimetry of MeV γ-rays converting to
Bernard
¹

2019
Nuclear Instruments and Methods in Physics Research Section A:
10
0
4
0
View full text Add to dashboard Cite