arXiv subjects

M. Ziegler

Publications and source records attributed to M. Ziegler.

22 records · Page 2Linked to original sources

arXiv2006

FUSE Spectroscopy of the DAO-type Central Star LS V+4621: Looking for the Photosphere in the Sea of Interstellar Absorption

The far-ultraviolet spectrum of the DAO White Dwarf LS V+4621, the exciting star of the possible planetary nebula Sh 2-216,is strongly contaminated by absorption features from the interstellar medium (ISM). For an ongoing spectral analysis, we aim to extract the pure photospheric spectrum in order to identify and model metal lines of species which are not detectable in the near-ultraviolet wavelength range. We have modeled the interstellar absorption precisely and considered it for the simulation of the FUSE (Far Ultraviolet Spectroscopic Explorer) observation. A state-of-the-art NLTE model-atmosphere spectrum which includes 16 elements is combined with the ISM absorption and then compared with the FUSE spectrum.

astro-ph↗

arXiv2002

Studies of aging and HV break down problems during development and operation of MSGC and GEM detectors for the Inner Tracking System of HERA-B

The results of five years of development of the inner tracking system of the HERA-B experiment and first experience from the data taking period of the year 2000 are reported. The system contains 184 chambers, covering a sensitive area of about 20 * 20 cm2 each. The detector is based on microstrip gas counters (MSGCs) with diamond like coated (DLC) glass wafers and gas electron multipliers (GEMs). The main problems in the development phase were gas discharges in intense hadron beams and aging in a high radiation dose environment. The observation of gas discharges which damage the electrode structure of the MSGC led to the addition of the GEM as a first amplification step. Spurious sparking at the GEM cannot be avoided completely. It does not affect the GEM itself but can produce secondary damage of the MSGC if the electric field between the GEM and the MSGC is above a threshold depending on operation conditions. We observed that aging does not only depend on the dose but also on the spot size of the irradiated area. Ar-DME mixtures had to be abandoned whereas a mixture of 70% Ar and 30% CO2 showed no serious aging effects up to about 40 mC/cm deposited charge on the anodes. X-ray measurements indicate that the DLC of the MSGC is deteriorated by the gas amplification process. As a consequence, long term gain variations are expected. The Inner Tracker has successfully participated in the data taking at HERA-B during summer 2000.

hep-ex↗

arXiv2000

A triple GEM detector with two dimensional readout

The triple GEM detector is a micropattern gas detector which consists of a primary ionisation gap and three consecutive gas electron multiplier (GEM) foils. A printed circuit board with readout strips detects the current induced by the drifting electron cloud originating from the last GEM stage. Thus the gas amplification and the signal readout are completely separated. Triple GEM detectors are being developed as a possible technology for the inner tracking in the LHCb experiment. In an earlier note we have reported first experience with such a detector in a test beam at PSI. Here we describe the construction of an improved version (thinner transfer gaps, segmented GEM foils, two dimensional readout). Results from performance measurements are presented using intense hadronic beams as well as cosmic ray data.

hep-ex↗

arXiv1998

Development of a Scintillatring Fibre Detector for HERA-B

A fibre detector with multianode PM readout for high rate applications was developed for the HERA-B spectometer to cover the area near the beampipe. Such a detector has to operate at particle rates up to 2*10**4 mm**(-2) s**(-1) and has to tolerate a radiation dosis up to 1 Mrad/y. The light output of test detectors with different scintillating fibres was measured as well as the light transport through clear fibres to the PM as a function of radiation dosis and different conditions of irradiation. The geometry of the detector is described and results for a full size prototype are presented.

hep-ex↗