A novel interferometric method is presented for the measurement of the absolute energy of electron beams. In the year 2016, a pioneering experiment was performed using a 195 MeV beam of the Mainz ...Microtron (MAMI). The experimental setup consisted of two collinear magnetic undulators as sources of coherent optical synchrotron light and a high-resolving grating monochromator. Beam energy measurements required the variation of the relative undulator distance in the decimeter range and the analysis of the intensity oscillation length in the interference spectrum. A statistical precision of 1 keV was achieved in 1 h of data taking, while systematic uncertainties of 700 keV were present in the experiment. These developments aim for a relative precision of 10−5 in the absolute momentum calibrations of spectrometers and high-precision hypernuclear experiments. Other electron accelerators with beam energies in this regime such as the Mainz Energy Recovering Superconducting Accelerator (MESA) might benefit from this new method.
The MAGIX focal plane time projection chamber Caiazza, S S; Achenbach, P; Aulenbacher, S ...
Journal of physics. Conference series,
04/2020, Letnik:
1498, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The MAGIX experiment is a versatile system optimized for low-energy nuclear and particle physics measurements. The setup is currently under development and will be installed at the MESA electron ...accelerator, at the Institute for Nuclear Physics of the University of Mainz. The main detectors of that experiment are a couple of high-precision magnetic spectrometers, each of them equipped with a GEM-based TPC at the focal plane to achieve a momentum resolution and angular resolution at the scattering vertex respectively of ≈δPP<10−4and≈1 1 mrad on scattered electron momenta between 1 MeV/c and 105 MeV/c. The limiting factor to achieve those results is the amount and uniformity of the material before the focal plane and even the presence of the TPC field cage can be relevant. Therefore we developed, and hereby introduce, an open field-cage TPC to fulfil those challenging requirements.
The quasifree
γ
→
d
→
π
0
n
(
p
)
photon beam asymmetry,
Σ
, has been measured at photon energies,
E
γ
, from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the ...first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49
∘
to 148
∘
. In this kinematic region, polarization observables are sensitive to contributions from the
Δ
(
1232
)
and
N
(1440) resonances. The extracted values of
Σ
have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID and Bonn–Gatchina analyses; while a revised SAID fit, including the new
Σ
measurements, has also been performed. In addition, isospin symmetry is examined as a way to predict
π
0
n
photoproduction observables, based on fits to published data in the channels
π
0
p
,
π
+
n
and
π
-
p
.
The quasifree
photon beam asymmetry,
, has been measured at photon energies,
, from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were ...collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49
to 148
. In this kinematic region, polarization observables are sensitive to contributions from the
and
(1440) resonances. The extracted values of
have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID and Bonn-Gatchina analyses; while a revised SAID fit, including the new
measurements, has also been performed. In addition, isospin symmetry is examined as a way to predict
photoproduction observables, based on fits to published data in the channels
,
and
.
The performance of solid-state photon detectors such as avalanche photodiodes or silicon photomultipliers (SiPMs) is strongly affected by temperature. Important device characteristics for the ...detection of low light levels or single photons are photon detection efficiency, dark noise, and gain. In the present work the C-series SiPMs from SensL was characterized in cryogenic environments. At 77 K the SiPMs proved to be an excellent choice for single photon detection and an operation point with minimum noise contributions was found. At 4 K the performance was degraded, exhibiting a smaller gain and a larger noise.
•SiPMs from SensL were characterized in cryogenic environments.•At 77 K the SiPMs proved to be an excellent choice for single photon detection.•At 4 K the performance was degraded, the SiPMs were exhibiting a smaller gain and a larger noise.
A low-noise and fast pre-amplifier and readout system for SiPMs Biroth, M.; Achenbach, P.; Downie, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2015, Letnik:
787
Journal Article
A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with ...a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: α_{E1}=10.99±0.16±0.47±0.17±0.34, β_{M1}=3.14±0.21±0.24±0.20±0.35; in units of 10^{-4} fm^{3} where the errors are statistical, systematic, spin polarizability dependent, and model dependent.
SiPM operation at cryogenic temperatures fails for many common devices. A particular type from Zecotek with deep channels in the silicon substrate instead of quenching resistors was tested at liquid ...helium temperature. Two similar types were thoroughly characterized from room temperature down to liquid nitrogen temperature by illuminating them with low light levels. At cryogenic temperatures the SiPMs show an unchanged rise-time and a fast recovery time, practically no after-pulses, and exhibit no increased cross-talk probability. Charge collection spectra were measured to extract the pixel gain and its variation, both comparable to room temperature at the same over-voltage. The quenching resistance was decreased at cryogenic temperature. It was found possible to use the characterized devices at temperatures of 1–4K for the read-out of a target at the Mainz Microtron in Germany.
The γ n → π 0 n differential cross section evaluated for 27 energy bins span the photon-energy range 290– 813 MeV (W = 1.195–1.553 GeV) and the pion c.m. polar production angles, ranging from 18° to ...162°, making use of model-dependent nuclear corrections to extract π0 production data on the neutron from measurements on the deuteron target. Additionally, the total photoabsorption cross section was measured. The tagged photon beam produced by the 883 MeV electron beam of the Mainz Microtron MAMI was used for the π0-meson production. Our accumulation of 3.6 × 106 γ n → π 0 n events allowed a detailed study of the reaction dynamics. Our data are in reasonable agreement with previous A2 measurements and extend them to lower energies. The data are compared with predictions of previous SAID, MAID, and BnGa partial-wave analyses and to the latest SAID fit MA19 that included our data. Selected photon-decay amplitudes N * → γ n at the resonance poles are determined for the first time.
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