Stefan Janos | University of Bern (original) (raw)

Papers by Stefan Janos

Journal of Instrumentation, 2009

Journal of Instrumentation, 2016

We present a study on the dependence of electric breakdown discharge properties on electrode geom... more We present a study on the dependence of electric breakdown discharge properties on electrode geometry and the breakdown field in liquid argon near its boiling point. The measurements were performed with a spherical cathode and a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of the time evolution of the breakdown volt-ampere characteristics was performed for the first time. It revealed a slow streamer development phase in the discharge. The results of a spectroscopic study of the visible light emission of the breakdowns complement the measurements. The light emission from the initial phase of the discharge is attributed to electro-luminescence of liquid argon following a current of drifting electrons. These results contribute to set benchmarks for breakdown-safe design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

Journal of Instrumentation, 2013

We report on the design, construction, and operation of a PID temperature controlled and vacuum t... more We report on the design, construction, and operation of a PID temperature controlled and vacuum tight camera casing. The camera casing contains a commercial digital camera and a lighting system. The design of the camera casing and its components are discussed in detail. Pictures taken by this cryo-camera while immersed in argon vapour and liquid nitrogen are presented. The cryo-camera can provide a live view inside cryogenic setups and allows to record video.

Journal of Instrumentation, 2013

Journal of Instrumentation, 2008

In this paper we report on the evidence for ionization track signals from cosmic ray muons and Co... more In this paper we report on the evidence for ionization track signals from cosmic ray muons and Compton electrons in a Time Projection Chamber (TPC) filled with liquid Argon and doped with different fractions of Nitrogen. This study has been conducted in view of the possible use of liquid Argon/Nitrogen TPCs for the detection of gamma rays in the resonant band of the Nitrogen absorbtion spectrum, a promising technology for security and medical applications.

ABSTRACT In this paper we report on the design, construction, and operation of a cryogenic system... more ABSTRACT In this paper we report on the design, construction, and operation of a cryogenic system designed to cool a Superheated Superconducting Granule (SSG) detector for dark matter search. The volume accommodating SSG detector is 20 cm in diameter and 67 cm long. The system provides a lowest operating temperature of 115 mK for long-lasting (several months) experiments in the Bern Underground Laboratory.

Czechoslovak Journal of Physics, 1989

ABSTRACT Thin superconducting films of Gd-Ba-Cu-O have been prepared on SrTiOâ, AlâOâ and ZrOâ su... more ABSTRACT Thin superconducting films of Gd-Ba-Cu-O have been prepared on SrTiOâ, AlâOâ and ZrOâ substrates by magnetron sputtering from single target of sintered material in an oxygen-argon atmosphere. The films were deposited at substrate temperatures between 770 and 850°C. In situ heat treatment at 400°C in pure Oâ atmosphere the films exhibited superconductivity with zero resistance transition temperatures 90.2, 91.5 and 89 Î for SrTiOâ, AlâOâ and ZrOâ substrates, respectively.

Zeitschrift für Physik B Condensed Matter, 1989

Positron annihilation measurements in the high T~ superconductors YBa2Cu3OT_ x have been performe... more Positron annihilation measurements in the high T~ superconductors YBa2Cu3OT_ x have been performed. The Doppler broaded annihilation line has been used for determination of the S parameter as a function of temperature between 13 and 100 K. Measurements from 80 to 100 K were performed at close temperature intervals and showed a resonance like change in S in a narrow temperature range near the transition temperature T~. Such behaviour of S can be linked to an anomalous change in the lattice parameter c. The second decrease of the S parameter was observed below 30 K.

Journal of the Less Common Metals, 1987

Physica Status Solidi (b), 1977

ABSTRACT The electrical resistivity temperature dependences of bulk and thin film samples of dysp... more ABSTRACT The electrical resistivity temperature dependences of bulk and thin film samples of dysprosium, samarium and thulium have been investigated in the temperature interval from 4.2 K to 300 K in the thickness range from 25 nm to 350 nm. A decrease of the Néel temperatures with decreasing film thickness has been observed for Dy and Sm thin films. The observed anomalies in resistivity vs. temperature dependences of Tm thin films have been caused by magnetic as well as by structural transitions due to the presence of hydrogen.

Acta Physica Slovaca - ACTA PHYS SLOVACA, 1976

Physica Status Solidi (a), 1972

Data on the thermal conductivity of thulium in thc range from 4 to 300 K have been presented in (... more Data on the thermal conductivity of thulium in thc range from 4 to 300 K have been presented in (1). The determination of the thermal conductivity of thulium below 1 K h a s not been reported yet.

Physica Status Solidi (a), 1971

Physica Status Solidi (a), 1974

Journal of Instrumentation, 2009

Journal of Instrumentation, 2016

We present a study on the dependence of electric breakdown discharge properties on electrode geom... more We present a study on the dependence of electric breakdown discharge properties on electrode geometry and the breakdown field in liquid argon near its boiling point. The measurements were performed with a spherical cathode and a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of the time evolution of the breakdown volt-ampere characteristics was performed for the first time. It revealed a slow streamer development phase in the discharge. The results of a spectroscopic study of the visible light emission of the breakdowns complement the measurements. The light emission from the initial phase of the discharge is attributed to electro-luminescence of liquid argon following a current of drifting electrons. These results contribute to set benchmarks for breakdown-safe design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

Journal of Instrumentation, 2013

We report on the design, construction, and operation of a PID temperature controlled and vacuum t... more We report on the design, construction, and operation of a PID temperature controlled and vacuum tight camera casing. The camera casing contains a commercial digital camera and a lighting system. The design of the camera casing and its components are discussed in detail. Pictures taken by this cryo-camera while immersed in argon vapour and liquid nitrogen are presented. The cryo-camera can provide a live view inside cryogenic setups and allows to record video.

Journal of Instrumentation, 2013

Journal of Instrumentation, 2008

In this paper we report on the evidence for ionization track signals from cosmic ray muons and Co... more In this paper we report on the evidence for ionization track signals from cosmic ray muons and Compton electrons in a Time Projection Chamber (TPC) filled with liquid Argon and doped with different fractions of Nitrogen. This study has been conducted in view of the possible use of liquid Argon/Nitrogen TPCs for the detection of gamma rays in the resonant band of the Nitrogen absorbtion spectrum, a promising technology for security and medical applications.

ABSTRACT In this paper we report on the design, construction, and operation of a cryogenic system... more ABSTRACT In this paper we report on the design, construction, and operation of a cryogenic system designed to cool a Superheated Superconducting Granule (SSG) detector for dark matter search. The volume accommodating SSG detector is 20 cm in diameter and 67 cm long. The system provides a lowest operating temperature of 115 mK for long-lasting (several months) experiments in the Bern Underground Laboratory.

Czechoslovak Journal of Physics, 1989

ABSTRACT Thin superconducting films of Gd-Ba-Cu-O have been prepared on SrTiOâ, AlâOâ and ZrOâ su... more ABSTRACT Thin superconducting films of Gd-Ba-Cu-O have been prepared on SrTiOâ, AlâOâ and ZrOâ substrates by magnetron sputtering from single target of sintered material in an oxygen-argon atmosphere. The films were deposited at substrate temperatures between 770 and 850°C. In situ heat treatment at 400°C in pure Oâ atmosphere the films exhibited superconductivity with zero resistance transition temperatures 90.2, 91.5 and 89 Î for SrTiOâ, AlâOâ and ZrOâ substrates, respectively.

Zeitschrift für Physik B Condensed Matter, 1989

Positron annihilation measurements in the high T~ superconductors YBa2Cu3OT_ x have been performe... more Positron annihilation measurements in the high T~ superconductors YBa2Cu3OT_ x have been performed. The Doppler broaded annihilation line has been used for determination of the S parameter as a function of temperature between 13 and 100 K. Measurements from 80 to 100 K were performed at close temperature intervals and showed a resonance like change in S in a narrow temperature range near the transition temperature T~. Such behaviour of S can be linked to an anomalous change in the lattice parameter c. The second decrease of the S parameter was observed below 30 K.

Journal of the Less Common Metals, 1987

Physica Status Solidi (b), 1977

ABSTRACT The electrical resistivity temperature dependences of bulk and thin film samples of dysp... more ABSTRACT The electrical resistivity temperature dependences of bulk and thin film samples of dysprosium, samarium and thulium have been investigated in the temperature interval from 4.2 K to 300 K in the thickness range from 25 nm to 350 nm. A decrease of the Néel temperatures with decreasing film thickness has been observed for Dy and Sm thin films. The observed anomalies in resistivity vs. temperature dependences of Tm thin films have been caused by magnetic as well as by structural transitions due to the presence of hydrogen.

Acta Physica Slovaca - ACTA PHYS SLOVACA, 1976

Physica Status Solidi (a), 1972

Data on the thermal conductivity of thulium in thc range from 4 to 300 K have been presented in (... more Data on the thermal conductivity of thulium in thc range from 4 to 300 K have been presented in (1). The determination of the thermal conductivity of thulium below 1 K h a s not been reported yet.

Physica Status Solidi (a), 1971

Physica Status Solidi (a), 1974