Submitted by khoukaz@uni-mue... on Mon, 29/07/2019 - 16:01.
The success of cluster-jet targets in hadron, lepton, and laser beam physics depends highlyon their performance. Therefore, a precise determination and optimisation of the targetproperties and understanding of the cluster formation process is essential.Within the work presented in this thesis, investigations and developments for andmeasurements using three different cluster-jet targets were performed: thePANDA cluster-jet target prototype for thePANDA experiment at FAIR, the MCT1S for CryoFlash atthe University of D ̈usseldorf and the jet target MCT-M for MAGIX at MESA.Laval nozzles, as key components of jet targets, originating from production processesdeveloped at the University of M ̈unster are reviewed with respect of their performance andbased upon that their developed processes were further improved yielding an optimisednozzle geometry, production processes, and a deeper insight into the complex clusterformation process.A new record hydrogen target thickness of(4.85±0.24)×10*15 atoms/cm*2 in a distanceof 2.1 m from the nozzle was achieved within this thesis work with thePANDA cluster-jettarget prototype.The high performance, state-of-the-art jet target for MAGIX at MESA was designed,built up, and set into operation. The suitability of a Mach-Zehnder interferometer toinvestigate the jet beam characteristics was shown and a well defined cluster beamwith a high range of constant target thickness of more than 30mmand a thickness of(2.1±0.2)×10*18 atoms/cm*2 directly behind the nozzle was recorded and the resultswere published [G+18]. Beam times at the MAinz MIcrotron results in elastic electron-proton cross sections and the feasibility to perform precise low energy physics like the determination of the proton radius using the jet target.The installation of a cluster-jet target at the high intensity ARCTURUS laser systemof the University of D ̈usseldorf resulted in accelerated protons with energies up to(88.0±14.5) keV, accelerated electrons, and X-rays within the framework of this thesis.Novel in this field is the stability and reproducibility of the accelerated particles. Moreover,a plasma temperature in the range of 1600 K to 4500 K by the cluster-laser interactionwith the U1 laser system was determined by the observation of Balmer spectral lines.Based on these successful results and the gained experience within this thesis, a newpowerful cluster-jet target was designed to perform extended measureme
Submitted by email@example.com... on Thu, 25/07/2019 - 12:02.
In high energy particle experiments one is interested in observables that require a transverse target polarization. The particle physics experiment PANDA consists of a detector at the particle accelerator FAIR currently under construction at GSI Helmholtz Centre for Heavy Ion Research, Darmstadt (GSI). The detector requires a high magnetic field in longitudinal direction with respect to the antiproton beam to provide high momentum resolution of the electrically charged particles. For the feasibility of a transverse polarized target in PANDA, it is essential to shield the longitudinal magnetic field.
The ability to shield an intense magnetic flux with a high temperature superconductor BSCCO in form of a shielding tube was investigated experimentally.
A shielding factor was extracted. A measurement of the stability of the shielding in time and a measurement of the residual magnetic
flux density along the axis of the tube was performed. A numerical simulation of the induced current in the shielding tube and the residual magnetic flux density along its axis was developed. The experimental results were compared to the predictions based on the numerical simulation. For the measurements a dedicated apparatus consisting of a cryostat, filled with liquid helium, at a temperature of 4.2 K was developed and constructed at the Helmholtz-Institut Mainz (HIM). The shielding tube was equipped with a movable Hall probe, with a Zero-eld Magnet on top. The external magnetic eld was generated by a purpose-built superconducting solenoid, which can be mounted on top of the shielding tube. An external magnetic flux density of 1 T was applied and shielded with
a shielding factor of at least 3:2 105 with a 95 % confidence level. In a measurement over four days a penetration of it into the shielding tube could
not be observed. The measurement of the residual magnetic flux density along the axis of the tube showed a shielding of the the central region of 80 mm (from total 150 mm shielding tube) up to 1 T. BSCCO is a good shielding material and can be used to shield the high magnetic field within the PANDA spectrometer.
Submitted by firstname.lastname@example.org on Mon, 03/06/2019 - 12:08.
The present thesis comprises two parts, in the first part a data sample of 1.31 billion J/ψ events recorded by the BESIII experiment has been used to analyze the hadronic decay J/ψ → φηη and in the second part calibration measurements of the temperature monitoring system for the electormagnetic calorimeter of the PANDA target spectrometer are evaluated.
Events of this decay pattern J/ψ → φηη with a final state consisting of a pair of charged kaons and four photons have been selected with an efficiency of about 12.5%. A partial wave analysis was performed with the PAWIAN softwarte and the information criteria BIC and AIC were used in an iterative approach to determine the hypotheses which optimally describe the data. The dynamics of scalar contributions are parameterized by a K-matrix with fixed pole positions and coupling strengths according to previous measurements. Utilizing Breit-Wigner functions to parameterize the dynamics of all other resonances, the hypothesis consisting of a (ππ) S-wave contribution as well as f2'(1525), f2(1810), ω2(1975), φ(1690), and h1(2215) resonances yields the best results. Additionally, hypotheses which use a K-matrix with released pole positions and coupling strengths to parameterize the dynamics of tensor contributions are tested. Scattering data from different measurements are used to constrain the K-matrix to reasonable parameter values. The best result is obtained for the hypothesis consisting of a K-matrix with three poles, (ππ) S-wave, ω2(1975), φ(1680), and h1(1965) contributions. Product branching fractions are determined for all contributions, most of them for the first time. For the f2'(1525) resonance, the branching fraction B(J/ψ → φ f2'(1525)) = (10.5 ± 0.6 stat ± 2.3 sys ) · 10^−4 is obtained, which is compatible with the result obtained by DM2 but not with the only other published value obtained by MARKII.
The electromagnetic calorimeter of the PANDA detector, which is currently under construction and will start data taking in 2025, is based on lead tungstate crystal scintillators. The operating temperature is chosen to be −25 °C in order to increase the light yield. To ensure the envisaged energy resolution, the temperature must be regulated precisely and monitored with a relative accuracy of 0.02 °C. Customized sensors and dedicated readout electronics have been developed to fulfill the strong requirements and are produced at Ruhr-Universität Bochum. Within the scope of this thesis numerous instances of both sensors and electronics have been calibrated to obtain an accurate readout chain. The hysteresis effect of the temperature sensors is taken into account by fitting the corresponding subsamples separately. The RMS of the differences between these fits and the data typically yields 0.01 °C. The typical hysteresis at −25 °C amounts to 0.03 °C. Several dedicated measurements have been performed to characterize the hysteresis effect. Furthermore, measures are taken to increase the production rate of accurate and reliable sensors and to obtain a high calibration throughput. The readout electronics, called THMP, is designed modularly so that it can read out several kinds of sensors, in particular resistance temperature sensors. Evaluating the calibrations of 10 devices with 64 readout channels each, a typical resistance uncertainty of 4 mΩ is determined, which is by a factor of two better than the design requirement. The reproducibility of the THMP calibrations is in the order of the requirement.
Submitted by s.a.kononov@inp... on Tue, 07/05/2019 - 14:40.
The PANDA detector at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR) in Darmstadt (Germany)
will address fundamental questions of hadron physics in high-energy antiproton collisions with fixed hydrogen and nuclear targets.
The PANDA Forward RICH (FRICH) is intended for identification of charged particles with forward polar angles below 5°–10°
and momenta from 3 to 15 GeV/c. PANDA FRICH will have a multilayer focusing aerogel radiator to achieve the required
resolution on Cherenkov angle. A set of precisely aligned flat mirrors will collect light on the multi-anode photomultipliers
which are located outside of the detector’s effective aperture. A baseline design of the PANDA Forward RICH is presented including results
of the full Monte-Carlo simulation, optical measurements and prototype beam tests.