Photon Tagging System Research Articles

High resolution micro-pattern gas detectors for particle physics

Micro-pattern gaseous detectors (MPGDs) allow operation at very high background particle flux with high efficiency and spatial resolution. This combination of parameters determines the main application of these detectors in particle physics experiments: precise tracking in the areas close to the beam and in the end-cap regions of general-purpose detectors. MPGDs of different configurations have been developed and are under development for several experiments in the Budker INP. The system of eight two-coordinate detectors based on a cascade of Gas Electron Multipliers (GEM) is working in the KEDR experiment at the VEPP-4M collider in the tagging system that detects electrons and positrons that lost their energy in two-photon interactions and left the equilibrium orbit due to a dedicated magnetic system. Another set of cascaded GEM detectors is developed for the almost-real Photon Tagging System (PTS) of the DEUTRON facility at the VEPP-3 storage ring. The PTS contains three very light detectors with very high spatial resolution (below 50 μm). Dedicated detectors based on cascaded GEMs are developed for the extracted electron beam facility at the VEPP-4M collider. These devices will allow precise particle tracking with minimal multiple scattering due to very low material content. An upgrade of the coordinate system of the CMD-3 detector at the VEPP-2000 collider is proposed on the basis of the resistive micro-WELL (μ-rWELL). A research activity on this subject has just started.

Threshold [formula omitted] photoproduction on transverse polarised protons at MAMI

Polarisation-dependent differential cross sections σT associated with the target asymmetry T have been measured for the reaction γp→→pπ0 with transverse target polarisation from π0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ball / TAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for σT have been used in combination with our previous measurements of the unpolarised cross section σ0 and the beam asymmetry Σ for a model-independent determination of S- and P-wave multipoles in the π0 threshold region, which includes for the first time a direct determination of the imaginary part of the E0+ multipole.

On-ground calibration of AGILE-GRID with a photon beam: results and lessons for the future

On the AGILE satellite, there is the Gamma Ray Imaging Detector (GRID) consisting of a Silicon Tracker (ST), a Cesium Iodide Mini-Calorimeter and an Anti-Coincidence system of plastic scintillator bars. The ST needs a calibration with a γ-ray beam to validate the simulation used to calculate the detector response versus the energy and the direction of the γ rays. A tagged γ-ray beam line was designed at the Beam Test Facility of the Laboratori Nazionali of Frascati, generated by an electron beam through bremsstrahlung in a position-sensitive target. The γ-ray energy is deduced by the difference with the post-bremsstrahlung electron energy [P. W. Cattaneo, et al., Characterization of a tagged γ-ray beam line at the daΦne beam test facility, Nucl. Instr. and Meth. A 674 (2012) 55–66; P. W. Cattaneo, et al., First results about on-ground calibration of the silicon tracker for the agile satellite, Nucl. Instr. and Meth. A 630(1) (2011) 251–257.]. The electron energy is measured by a spectrometer consisting of a dipole magnet and an array of position sensitive silicon strip detectors, the Photon Tagging System (PTS). In this paper the setup and the calibration of AGILE performed in 2005 are described.

Characterization of a tagged [formula omitted] beam line at the [formula omitted] Beam Test Facility

At the core of the AGILE scientific instrument, designed to operate on a satellite, there is the Gamma Ray Imaging Detector (GRID) consisting of a Silicon Tracker (ST), a Cesium Iodide Mini-Calorimeter and an Anti-Coincidence system of plastic scintillator bars. The ST needs an on-ground calibration with a γ-ray beam to validate the simulation used to calculate the energy response function and the effective area versus the energy and the direction of the γ rays. A tagged γ-ray beam line was designed at the Beam Test Facility (BTF) of the INFN Laboratori Nazionali of Frascati (LNF), based on an electron beam generating γ-rays through bremsstrahlung in a position-sensitive target. The γ-ray energy is deduced by difference with the post-bremsstrahlung electron energy [1,2]. The electron energy is measured by a spectrometer consisting of a dipole magnet and an array of position sensitive silicon strip detectors, the Photon Tagging System (PTS). The use of the combined BTF-PTS system as tagged photon beam requires understanding the efficiency of γ-ray tagging, the probability of fake tagging, the energy resolution and the relation of the PTS hit position versus the γ-ray energy. This paper describes this study comparing data taken during the AGILE calibration occurred in 2005 with simulation.

Experiments with internal targets at the VEPP-3 electron storage ring

An overview of the recently completed, current, and planned experiments with internal targets at the VEPP-3 electron-positron storage ring in Novosibirsk is given. The results of the experiment to separately measure the deuteron form factors in elastic ed scattering in the range of momentum transfer Q 2 = 8−15 fm−2 are provided. The results of measuring the tensor analyzing power components of the tensor-polarized deuteron photodisintegration reaction in the range of γ-quantum energies E γ = 25−600 MeV are presented. The tensor analyzing powers of the coherent photoproduction of a neutral pion on a tensor-polarized deuteron have been measured for the first time. The almost-real photon tagging system being created is discussed. The status of the experiment under way to determine the contribution of two-photon exchange to the elastic ep scattering cross section is described.

The second GeV tagged photon beamline at ELPH

The second GeV bremsstrahlung photon beamline has been constructed for meson photo-production experiments at Research Center for Electron Photon Science, Tohoku University, where a 1200MeV electron synchrotron called STretcher Booster (STB) has been in operation primarily for Quark Nuclear Physics. An internal radiator is employed to produce the bremsstrahlung photon beam out of circulating electrons in the STB ring. A photon tagging system is placed inside one of the bending magnets of the ring. The tagged energy of the photon beam ranges from 740 to 1150MeV for 1200MeV operation of the STB synchrotron. The details of the tagging system and the characteristics of the photon beam are described.

Energy calibration of tagged photons by the d(γ,π−pp) reaction

The energy of tagged photons, which were provided from the internal photon tagging system of the Laboratory of Nuclear Science, Tohoku University, has been calibrated using the d(γ,π−pp) reaction. Charged pions and protons in the final state were detected with the Neutral Kaon Spectrometer (NKS2). Photon energies were obtained from the reaction of d(γ,π−pp). The derived photon energy was consistent with the design of the tagger system and the previous measurement using electron-positron pair production. The consistency demonstrates the performance of NKS2 and the capability of the photon energy calibration using d(γ,π−pp).

200-MeV bremsstrahlung tagged photon beams at Sendai

A new beam line for photonuclear reaction experiments using tagged photons has been constructed to take advantage of the completion of the 1.2-GeV STretcher Booster (STB) ring at the Laboratory of Nuclear Science (LNS), Tohoku University. A photon tagging system was installed at the end of the new beam line. It provides bremsstrahlung tagged photon beams in an energy range from 0.2 E 0 to 0.8 E 0 MeV at the incident electron energy E 0 with an energy resolution of Δ E / E ≈ 10 - 2 . The tagged photon intensity I ⩽ 5 × 10 6 photons / s is available for typical photonuclear reaction experiments. We introduce the basic parameters of the tagged photons by showing the commissioning data.

The 1.2 GeV photon tagging system at LNS-Tohoku

A tagged photon beam line has been constructed in the Stretcher–Booster ring (STB ring) at Tohoku University. The quasi-monochromatic photon beam is produced by the internal photon tagging system which consists of a solid fiber radiator and the compact tagging counter installed in a bending magnet of the STB ring. The energy range of the tagged photon is from 0.8 to 1.1 GeV with the electron energy of 1.2 GeV . The performance of the tagging system has been investigated. The system provides good quality of γ -rays for the nuclear and hadron physics experiments.

A photon tagging system for the GDH-Experiment at ELSA

Abstract This paper describes the set-up and calibration of the tagging system of the GDH-Experiment at the accelerator facility E lsa in Bonn. The system consists of a C-type dipole magnet and a hodoscope of 65 scintillation counters which are operated pairwise in coincidence to form 64 tagging channels. Photons can be tagged in a range of 68–97% of the primary electron energy E0. The energy resolution ranges from 0.2% to 0.6% of E0. The time resolution is better than 165 ps . The system was operated at rates up to 5×10 6 photons/s in the full tagged energy range. The energy dependence of the photon definition probability was determined using several different methods and was found to agree well with calculations.

The bremsstrahlung tagged photon beam in Hall B at JLab

We describe the design and commissioning of the photon tagging beamline installed in experimental Hall B at the Thomas Jefferson National Accelerator Facility (JLab). This system can tag photon energies over a range from 20% to 95% of the incident electron energy, and is capable of operation with beam energies up to 6.1 GeV. A single dipole magnet is combined with a hodoscope containing two planar arrays of plastic scintillators to detect energy-degraded electrons from a thin bremsstrahlung radiator. The first layer of 384 partially overlapping small scintillators provides photon energy resolution, while the second layer of 61 larger scintillators provides the timing resolution necessary to form a coincidence with the corresponding nuclear interaction triggered by the tagged photon. The definitions of overlap channels in the first counter plane and of geometric correlation between the two planes are determined using digitized time information from the individual counters. Auxiliary beamline devices are briefly described, and performance results to date under real operating conditions are presented. The entire photon-tagging system has met or exceeded its design goals.

Absolute linear polarization gauge for low-energy photons

The Σ-asymmetry of the reaction γ → + 12 C→ 8Be+ 4He→3α , through 8 Be in the ground state is shown to be unity. We present an experimental setup, based on an arrangement of silicon detectors associated with a photon tagging system, which is able to extract the 8 Be ground state events from the total reaction yield. The use of such a setup as an absolute gauge for the degree of linear polarization of a photon beam was studied by Monte Carlo simulation.

A composite thin vacuum window for the CLAS photon tagger at Jefferson lab

The construction of a thin vacuum window, currently in use on the CLAS photon tagging system at the Thomas Jefferson National Accelerator Facility, is described. A layer of woven Kevlar cloth supports a much thinner membrane of aluminized Mylar. Notable features of this particular window include its overall length (9.6 m), and the fact that the entire load is supported by the epoxy seal with no mechanical clamping around the edges. Results from a diverse program of materials testing, including a clear dependence of leak rate on relative humidity, are also reported.

The photon tagging system of the PHOENICS-experiment at ELSA

This paper describes the setup and the first test of the tagging system of the PHOENICS experiment at the electron stretcher ELSA in Bonn. The system covers the energy range k = 200–950 MeV simultaneously with an energy resolution of 5–10 MeV (FWHM). The tagging system is in operation since early 1990 and has been successfully used in first measurements of γp → π +n and for η-production from proton and deuterium targets.

The 150-MeV photon tagging system at Sendai

A description is given of the 32-channel photon tagging system recently constructed at the Laboratory of Nuclear Science. Tohoku University. Some results of photonuclear experiments performed using this system in conjunction with the high duty factor electron beam from the pulsed beam stretcher are presented.

A tagged photon spectrometer for the mainz 180 MeV microtron

A photon tagging system has been installed on the 180 MeV electron microtron at the Institut fuer Kernphysik in Mainz for use in experiments on photonuclear reactions at intermediate energies. The system enables Bremsstrahlung produced photons in the energy range 80-174 MeV to be tagged at rates up to 5x107s-l with an overall efficiency of around 60-65%.

A tagged photon spectrometer for use with the mainz 180 MeV microtron

This paper describes a photon tagging system which has been installed on the 180 MeV electron microtron at the Institut fur Kernphysik in Mainz for use in experiments on photonuclear reactions at intermediate energies. The system enables bremsstrahlung produced photons in the energy range 80–174 MeV to be tagged at rates up to 5×107 s−1.

Photon Tagging System at the INS Electron Synchrotron

A photon tagging system which determines the energy of each photon in the bremsstrahlung process is constructed, and is tested using an extracted electron beam from the 1.3 GeV electron synchrotron at the Institute for Nuclear Study, University of Tokyo. The system which consists of an analyzing magnet and twenty-five tagging counters detects the recoil electrons in the energy range from 100 MeV to 350 MeV. The energy of each tagged photon has been calibrated with a total absorption type lead glass Cerenkov counter. A good agreement within the error of ±10 MeV is obtained between the energy measured by the Cerenkov counter and the one calculated from the trajectory of the recoil electron. From the first experiment using this system, it is found that the intensity of the tagged photon beam is limited to 105 photons/s.

A high resolution photon tagging system in the GeV region

A photon tagging system which measures the energy of photons in a bremsstrahlung spectrum is described. The apparatus covers a photon energy range of 2 GeV starting 160 MeV below the energy of the incident electron beam. 192 counters provide a nominal resolution between 6 MeV for a photon energy 160 MeV below the incident electron energy and 11 MeV for a photon energy 2160 MeV below the incident electron energy.

The total pair production cross section of γ-rays in hydrogen and deuterium

The total electromagnetic cross sections of g-rays in hydrogen and deuterium have been measured over the energy range 265–4215 MeV using a photon tagging system. From these measurements, the total pair production cross sections are obtained, and the results are found to be in good agreement with the predictions of Jost, Luttinger and Slotnick.