ALICE (A Large Ion Collider Experiment) is the dedicated heavy ion experiment at the Large Hadron Collider at CERN. The main tracking device of ALICE is a large volume TPC.
The milestones of the TPC ...commissioning as well as the current status of the detector calibration are presented. The obtained resolutions in transverse momentum, position as well as in specific energy loss (dE/dx) are presented and results from noise and electron drift velocity measurements are addressed.
A novel method to determine the total hydrogen density and, accordingly, a precise plasma temperature in a lowly ionized hydrogen plasma is described. The key to the method is to analyze the energy ...loss of swift heavy ions interacting with the respective bound and free electrons of the plasma. A slowly developing and lowly ionized hydrogen theta-pinch plasma is prepared. A Boltzmann plot of the hydrogen Balmer series and the Stark broadening of the H_{β} line preliminarily defines the plasma with a free electron density of (1.9±0.1)×10^{16} cm^{-3} and a free electron temperature of 0.8-1.3 eV. The temperature uncertainty results in a wide hydrogen density, ranging from 2.3×10^{16} to 7.8×10^{18} cm^{-3}. A 108 MHz pulsed beam of ^{48}Ca^{10+} with a velocity of 3.652 MeV/u is used as a probe to measure the total energy loss of the beam ions. Subtracting the calculated energy loss due to free electrons, the energy loss due to bound electrons is obtained, which linearly depends on the bound electron density. The total hydrogen density is thus determined as (1.9±0.7)×10^{17} cm^{-3}, and the free electron temperature can be precisely derived as 1.01±0.04 eV. This method should prove useful in many studies, e.g., inertial confinement fusion or warm dense matter.
The triple GEM detectors for the CBM muon chamber (MuCh) will be operated in a high rate environment of heavily ionizing particles due to the presence of thick iron absorber in the system. Therefore, ...the stability of the detectors needs to be tested. In a dedicated beam time double mask triple GEM detectors have been tested at CERN SPS/H4. In this study pion beam of ~ 150GeV/c has been used. Different methods to determine the spark has been described in this paper. The stability of the triple GEM detector setup in an environment of high energetic showers is studied. To this end the spark probability in a shower environment is compared to the spark probability in a pion beam. The spark probability was found to be ~10−7 in a high momentum pion beam and in an induced particle shower.
We present experimental results of two head-on colliding plasma sheaths accelerated by pulsed-power-driven coaxial plasma accelerators. The measurements have been performed in a small vacuum chamber ...with a neutral-gas prefill of ArH2 at gas pressures between 17 Pa and 400 Pa and load voltages between 4 kV and 9 kV. As the plasma sheaths collide, the electron density is significantly increased. The electron density reaches maximum values of ≈8 ⋅ 1015 cm−3 for a single accelerated plasma and a maximum value of ≈2.6 ⋅ 1016 cm−3 for the plasma collision. Overall a raise of the plasma density by a factor of 1.3 to 3.8 has been achieved. A scaling behavior has been derived from the values of the electron density which shows a disproportionately high increase of the electron density of the collisional case for higher applied voltages in comparison to a single accelerated plasma. Sequences of the plasma collision have been taken, using a fast framing camera to study the plasma dynamics. These sequences indicate a maximum collision velocity of 34 km/s.
The characteristics of triple GEM detectors have been studied systematically by using cosmic ray muons. The minimum ionizing particle (MIP) spectra have been taken for different GEM voltage setting. ...Efficiency of GEM detector has been measured for cosmic ray. At high rate operation of GEMs the value of the protection resistor influences the gain and the stability. This feature has been investigated varying both the rate and the value of the protection resistor. This measurement has been performed using both X-ray generator and Fe super(55) source. The ageing and long-term stability of GEM based detectors has been studied employing both X-ray generator and Fe super(55) source. The ageing study of one GEM module is performed by using a 8 keV Cu X-ray generator to verify the stability and integrity of the GEM detectors over a longer period of time. The accumulated charge on the detector is calculated from the rate of the X-ray and the average gain of the detector. The details of the measurement and results has been described in this article.
Heating of low-density CHO-foam layers by means of soft X-rays Rosmej, O.N.; Bagnoud, V.; Eisenbarth, U. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2011, Letnik:
653, Številka:
1
Journal Article
Recenzirano
Interaction of soft X-ray thermal radiation with polymer foam layers has been studied experimentally. Indirectly heated CHO-foams were used to create a plasma target for applications in combined ...heavy ion beam-laser experiments that are aimed at investigation of the heavy ion energy loss in ionized matter. In this work, we report experimental results on heating of low Z foams by means of the Planckian radiation generated in gold hohlraums. The experimental goal was to study the hohlraum radiation field, duration of the soft X-ray pulse, the conversion efficiency of the laser energy into soft X-rays, measurements of the absorption properties of foam layers and parameters of the foam targets heated by the Plankian radiation.
The N/Z dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at the GSI Schwerionen Synchrotron (SIS). Stable and radioactive Sn and ...La beams with an incident energy of 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. For the interpretation of the data, calculations with the statistical multifragmentation model for a properly chosen ensemble of excited sources were performed. The parameters of the ensemble, representing the variety of excited spectator nuclei expected in a participant-spectator scenario, are determined empirically by searching for an optimum reproduction of the measured fragment-charge distributions and correlations. An overall very good agreement is obtained. The possible modification of the liquid-drop parameters of the fragment description in the hot freeze-out environment is studied, and a significant reduction of the symmetry-term coefficient is found necessary to reproduce the mean neutron-to-proton ratios /Z and the isoscaling parameters of Z{<=}10 fragments. The calculations are, furthermore, used to address open questions regarding the modification of the surface-term coefficient at freeze-out, the N/Z dependence of the nuclear caloric curve, and the isotopic evolution of the spectator system between its formation during the initial cascade stage of the reaction and its subsequent breakup.
After the spherical theta pinch had been developed at the Institute of Applied Physics in Frankfurt, considerable progress in creating high efficiency and long lifetime plasma sources had been made. ...Several devices have been built to study the characteristics of the spherically confined plasma. Scaling rules and investigated setups are presented, showing devices with electron densities of up to some 10 23 m -3 , electron temperatures of several eV and confinement times of ~10 μs. Typical dimensions are: discharge vessel radius R = 10 cm, radius of the pinched plasma r = 2 cm, initial gas pressures of 1-200 Pa at currents of up to 35 kA and resonance frequencies of 10-40 kHz. During the harmonic discharge of the stored energy, the plasma periodically pinches and expands again as long as the current rise rate creates sufficient electrical field strengths for ionization, which allows for pinching sequences in the millisecond range. The principles, improvements, theoretical approaches, and applications including pulsed ion source, plasma ion stripping, and vacuum ultraviolet flash lighting are discussed.
Systematic studies on the gain and the energy resolution have been carried out by varying the voltage across the GEM foils for both single mask and double mask triple GEM detector prototypes. ...Variation of the gain and the energy resolution has also been measured by varying either the drift voltage, transfer voltage and induction voltage keeping other voltages constant. The results of the systematic measurements have been presented.
The Facility for Antiproton and Ion Research (FAIR) is a new international accelerator laboratory at the GSI in Darmstadt, Germany. The main topic at this facility is aimed to heavy ion research. The ...FAIR project in comparison to the existing facility GSI extends the research area by raising the energy of heavy ion beams. The demand for acceleration of the beam to the highest possible energy is a highly ionized charge state of the Ion beam. For beam stripping to get higher charge state, the traditional tools are foil stripper and gas stripper. Hence pulsed Plasma is suggested to be a stripper medium. In Frankfurt are different kinds of Pinch Plasmas under investigation for this application. One is a Spherical Theta Pinch and the other a hollow cathode Screw Pinch 1 . The screw pinch plasma consists of a superposition of a linear Zpinch and a Theta pinch. The constricting effect on the plasma or conductor is produced by the magnetic field pressure resulting from the magnetic field of the linear current and magnetic field of the coil. The device operates at a frequency of approximate 14 kHz and with a capacity of 34 \mu \mathrm {F}. This contribution gives the first results of the transfer efficiency and optical investigations of pulsed the screw pinch compared to a theta pinch 2 . In addition first measurements of beam time experiments at GSI will be presented.
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