12 research outputs found
Quasi-free Photoproduction of η-Mesons off 2H and 3He
In this work, we are presenting a combination of two preliminary results for quasi-free photoproduction of η-mesons from the liquid deuterium and 3He targets for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI electron accelerator, using the Glasgow tagged photon facility. Decay photons of the η-mesons and the recoil nucleons were detected with an almost 4π covering electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets show a narrow structure in the excitation function of γ + n → n + η. The results from the two measurements are consistent within the expected effects from nuclear Fermi motion
Development of a multi-channel power supply for silicon photo-multipliers used with inorganic scintillators
The motivation of the current R&D project is based upon the requirements of
the JEDI international collaboration aiming to measure Electric Dipole Moments
(EDMs) of charged particles in storage rings. One of the most important
elements of such an experiment will be a specially designed polarimeter with
the detection system based on a modular inorganic scintillator (LYSO crystal)
calorimeter. The calorimeter modules are read out by Silicon Photo Multipliers
(SiPMs). This paper describes the development of a multi-channel power supply
for the polarimeter modules, providing very stable and clean bias voltages for
SiPMs. In order to ensure the best possible performance of SiPMs in conjunction
with the crystal-based calorimeter modules and to guarantee the required level
of calorimeter stability, several quality requirements have to be met by the
power supply. Additionally, it is required to provide features including remote
control via the network, ramping of the output voltage, measuring and sending
the information about its output voltages and currents, etc. The obtained
results demonstrate that the goals for the JEDI polarimeter are met. The
developed hardware will be useful in other fields of fundamental and applied
research, medical diagnostic techniques and industry, where SiPMs are used
First Search for Axion-Like Particles in a Storage Ring Using a Polarized Deuteron Beam
Based on the notion that the local dark-matter field of axions or axion-like
particles (ALPs) in our Galaxy induces oscillating couplings to the spins of
nucleons and nuclei (via the electric dipole moment of the latter and/or the
paramagnetic axion-wind effect), we performed the first experiment to search
for ALPs using a storage ring. For that purpose, we used an in-plane polarized
deuteron beam stored at the Cooler Synchrotron COSY, scanning momenta near 970
MeV/c. This entailed a scan of the spin precession frequency. At resonance
between the spin precession frequency of deuterons and the ALP-induced EDM
oscillation frequency there will be an accumulation of the polarization
component out of the ring plane. Since the axion frequency is unknown, the
momentum of the beam and consequently the spin precession frequency were ramped
to search for a vertical polarization change that would occur when the
resonance is crossed. At COSY, four beam bunches with different polarization
directions were used to make sure that no resonance was missed because of the
unknown relative phase between the polarization precession and the axion/ALP
field. A frequency window of 1.5-kHz width around the spin precession frequency
of 121 kHz was scanned. We describe the experimental procedure and a test of
the methodology with the help of a radiofrequency Wien filter located on the
COSY ring. No ALP resonance was observed. As a consequence an upper limit of
the oscillating EDM component of the deuteron as well as its axion coupling
constants are provided.Comment: 25 pages, 24 figures, 7 tables, 67 reference
LYSO crystal testing for an EDM polarimeter
Four detector modules, built from three different LYSO crystals and two different types of light sensors (PMTs and SiPM arrays), have been tested with a deuteron beam from 100 MeV – 270 MeV at the COSY accelerator facility for the srEDM project at the Forschungszentrum Jülich in Germany. The detector modules were arranged in a cluster and mounted on a positioning table. The deuteron beam was targeted at the center of each individual crystal for data analysis. The signals were digitized using a 14 bit, 250 MS/s flash ADC. Further, the energy spectra were calibrated using the known beam energies from the accelerator. From the calibrated spectra, the energy resolution was calculated. A resolution of 3% for the low energies and down to 1% for the high energy of 270 MeV was achieved. A deuteron reconstruction efficiency of almost 100% for low energies and around 70% for high energies was achieved. The SiPM light sensor showed a very good performance and will be used for the next generation of detector modules
A new approach to use LYSO scintillators for polarimetry in the storage ring EDM measurements
One of the fundamental questions of modern particle physics is the existence of finite electricdipole moments (EDM) of the hadrons. In case of charged particles, like protons and deuterons,the proposed method is the precise determination of the precession of the beam polarization vec-tor in a storage ring. For that purpose, the JEDI (Jülich Electric Dipole moment Investigations)collaboration is developing a precise polarimeter detector based on LYSO scintillator coupled toSiPM modules. They are capable of stopping almost 300 MeV elastically scattered deuterons andprotons. Measuring the kinetic energy of the scattered projectiles ensures the accurate reactionidentification leading to a precise polarization determination.To create the long-term reliable detector system, we have performed four iterations of the detec-tor development (three of them since last CALOR 2016). Currently, we are operating 52 LYSOmodules with a dedicated dead-time less sampling ADC readout system. The modules are verycompact, due to modern high pixel density SiPM readout. A summary of all test beam times andthe accumulated experience will be presented and discussed
Storage Ring to Search for Electric Dipole Moments of Charged Particles -- Feasibility Study
The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly helium-3) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10 ecm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. It foresees a step-wise plan, starting with ongoing COSY (Cooler Synchrotron, Forschungszentrum J\'ulich) activities that demonstrate technical feasibility. Achievements to date include reduced polarisation measurement errors, long horizontal-plane polarisation lifetimes, and control of the polarisation direction through feedback from the scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally the high precision electric-field storage ring