Fri·Aug 7, 2015Friday·August 7, 2015

1. 01*

   Neutral multi-MeV/u particles from laser-induced processes in ultra-dense deuterium D(0): accurate two-collector timing and magnetic analysis

   Leif Holmlid

   Laser-induced processes in ultra-dense deuterium D(0) layers eject multi-MeV u-1 particles using ns laser pulse energies of <200 mJ. Such particles have been observed previously as mA currents to time-of-flight (TOF) collectors at up to 1 m distance. The signal current is mainly due to the ejection of secondary electrons by impinging MeV particles on the collectors. Improved two-collector time-of-flight measurements now show that the energy of the particles is in the range 1-50 MeV u-1. Their distributions are almost thermal at up to 13 MeV u-1 or are sharper than thermal. The fastest sharp peak may indicate shock-wave acceleration by many-body energy transfer. A magnetic field of 0.4 T deflects only a small part of the multi-MeV particle flux which thus mainly consists of neutral particles. By combining the TOF method with magnetic deflection, it is ascertained that the multi-MeV particles are studied and not any slower particle emission from the target. The neutral multi-MeV particles are concluded to be fragments of ultra-dense hydrogen HN(0) as observed in other experiments.

   nucl-exphysics.ins-det0 citations
2. 02*

   Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

   Andrew J. R. Puckett🇺🇸

   The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electron-nucleon scattering. These form factors are functions of the squared four-momentum transfer $Q^2$ between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH${}_2$ analyzers. The scattered electron was detected in a large-acceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors $G_E^p/G_M^p$. The measurements reported in this thesis took place at $Q^2=$5.2, 6.7, and 8.5 GeV${}^2$, and represent the most accurate measurements of $G_E^p$ in this $Q^2$ region to date.

   nucl-exhep-exphysics.ins-det14 citations
3. 03*

   A performance study of an electron-tracking Compton camera with a compact system for environmental gamma-ray observation

   Tetsuya Mizumoto🇯🇵 · Dai Tomono🇯🇵 · Atsushi Takada🇯🇵 · Toru Tanimori🇯🇵 · Shotaro Komura🇯🇵 · Hidetoshi Kubo🇯🇵 · Yoshihiro Matsuoka🇯🇵 · Yoshitaka Mizumura🇯🇵 · Kiseki Nakamura🇯🇵 · Shogo Nakamura🇯🇵 · Makoto Oda🇯🇵 · Joseph D. Parker🇯🇵 and 3 other authors

   An electron-tracking Compton camera (ETCC) is a detector that can determine the arrival direction and energy of incident sub-MeV/MeV gamma-ray events on an event-by-event basis. It is a hybrid detector consisting of a gaseous time projection chamber (TPC), that is the Compton-scattering target and the tracker of recoil electrons, and a position-sensitive scintillation camera that absorbs of the scattered gamma rays, to measure gamma rays in the environment from contaminated soil. To measure of environmental gamma rays from soil contaminated with radioactive cesium (Cs), we developed a portable battery-powered ETCC system with a compact readout circuit and data-acquisition system for the SMILE-II experiment. We checked the gamma-ray imaging ability and ETCC performance in the laboratory by using several gamma-ray point sources. The performance test indicates that the field of view (FoV) of the detector is about 1sr and that the detection efficiency and angular resolution for 662keV gamma rays from the center of the FoV is $(9.31\pm 0.95)\times 10^{{}^{-}5}$ and $5.9^{\circ }\pm 0.6^{\circ }$, respectively. Furthermore, the ETCC can detect 0.15$\mu Sv/h$ from a ${}^{137}$Cs gamma-ray source with a significance of 5$\sigma$ in 13 min in the laboratory. In this paper, we report the specifications of the ETCC and the results of the performance tests. Furthermore, we discuss its potential use for environmental gamma-ray measurements.

   ↳ physics.ins-detastro-ph.IMhep-exnucl-exJINST(2015)·6 citations
4. 04*

   A versatile DAQ, monitoring and data processing system for nuclear experiments in CAMAC and VME standards

   Zdenek Hons

   Common and unique features of nuclear physics measurements are examined. Such analysis with respect to existing hardware and software platforms and standards allows to algorithmize the DAQ, monitoring and processing tasks. A universal measurement framework is proposed and programmed. It allows to implement various measurement setups via a configuration file where special features are described by a simple language. An abstract description of the experimental data is introduced and a unified data format is proposed to hide data structures resulting from the various measurement setups. A simple language is developed to describe processing and visualizing the unified data via histograms. A universal processing engine is developed which creates histograms based on requirements described in a configuration file.

   ↳ physics.ins-detnucl-ex6 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.