B2 – Publications | Institute for Nuclear Physics

Here you can find a chronological list of publications, which resulted from the work of the B2 collaboration. Click on a publication to get an abstract and a link to the article.

Publications in journals

Polarized beams for electron accelerators
→ Eur. Phys. J. Special Topics 198, 361 (2011)

The MAMI-C accelerator
→ Eur. Phys. J. Special Topics 198, 19 (2011)

Opportunities for parity violating electron scattering experiments at the planned MESA facility Accepted for publication in Hyperfine Interactions
→ Online: Doi 10.1007/s10751-011-0269-9 (2011)

A Mott polarimeter operating at MeV electron beam energies
→ Review of Scientific Instruments (82) 033303 (2011)

Operation of the MAMI accelerator with a Wien filter based spin rotation system
→ Nuclear Instruments and Methods in Physics Research A 568, pp. 537–542 (2006)

First attempt of the measurement of the beam polarization at an accelerator with the optical electron polarimeter POLO
→ Nuclear Instruments and Methods in Physics Research A 534, pp. 361–370 (2004)

Pulse response of thin III/V semiconductor photocathodes
→ Journal of Applied Physics - Volume 92, Issue 12, pp. 7536-7543 (2002)

Publications in conference reports
High average photocurrent research at MAMI
→ J. Phys.: Conf. Ser. 298 (2011)

Hydrogen cleaning of superlattice photocathodes.
→ AIP Conf.Proc.1149 (2009)

Ab initio calculation of effective sherman functions in MeV Mott scattering
→ AIP Conf.Proc.1149 (2009)

Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice with Distributed Bragg Reflector
→ SLAC-PUB-12980 (2007)

Polarized electron source operation at average currents of several milliamperes
→ American Institute of Physics conference proceedings vol.915 (2007)

Summary of the Workshop on Spin Polarized Electron Sources and Polarimeters
→ SPIN 2004, World scientifc, (Singapore) p. 215-220 (2005)

Photocathode life time research at MAMI
→ SPIN 2004, World scientifc, (Singapore) p. 975-979 (2005)

Time resolved depolarization measurements on superlattices with strained wells
→ SPIN 2004, World scientifc, (Singapore) p. 921-925 (2005)

Status of the polarized source at MAMI
→ American Institute of Physics conference proceedings vol.675 (2003)

Spin manipulation at MAMI-C
→ Proceedings of the 8th European accelerator conference, p.1816 (2002)

Development of an optical electron polarimeter with Argon gas
→ Proceedings of the 8th European accelerator conference, p.1861 (2002)

The European Physical Journal-Special Topics (2011)
Polarized beams for electron accelerators

Abstract. NEA-GaAs based photocathodes allow the production of spin-polarized electron beams for fundamental research. We demonstrate how semiconductor properties influence salient parameters such as polarization and beam brightness. We present techniques that provide remedies for the extreme sensitivity to environmental factors. These are discussed for the specific installation that has provided spinpolarized beam at the MAMI facility during the last decade.

K. Aulenbacher
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany

The European Physical Journal-Special Topics (2011)
The MAMI C accelerator

Abstract. The demand for CW electron beam energies of more than 1 GeV led to the decision of constructing a worldwide unique accelerator – the Harmonic Double-Sided Microtron (HDSM). This machine nearly doubles the beam energy of the Mainz Microtron cascade from up to 855MeV to now 1.6 GeV to extend the experimental capabilities for nuclear and particle physics experiments to higher excitation energies. For the recent decade the construction and commissioning of the HDSM at the Institut f¨ur Kernphysik has been the major task of the accelerator department.

M. Dehn, K. Aulenbacher, R. Heine, H. -J. Kreidel, U. Ludwig-Mertin und A. Jankowiak
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany

Hyperfine Interactions Volume 200, Numbers 1-3, 3-7 (2011)
Opportunities for parity violating electron scattering experiments at the planned MESA facility

Abstract. We suggest to start an accelerator physics project called the Mainz Energy recovering Superconducting Accelerator (MESA) as an extension to our experimental facilities. MESA may allow to introduce an innovative internal target regime based on the ERL principle. A second mode of operation will be to use an external polarized electron beam for parity violating experiments.

K. Aulenbacher
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany

Review of Scientific Instruments (82) 033303 (2011)
A Mott polarimeter operating at MeV electron beam energies

accepted: 29 January 2011
published online: 14 March 2011

Abstract. We have developed a Mott electron polarimeter for the Mainzer microtron (MAMI) accelerator in Mainz, Germany. At beam energies ranging between 1.0 and 3.5 MeV two double focusing magnet spectrometers collect elastically backscattered electrons from gold targets. In spite of the small spectrometer acceptance, a sufficient statistical efficiency is achieved to provide very fast measurements if beam currents typical for experiments at MAMI are being used. High reproducibility is achieved, demonstrating that the results of asymmetry measurements are independent of the primary beam current in a range from 0.004 to 45 µA at a level of <1% relative variation. Combared to low energy polarimeters of similar construction an improvement of a factor 2-3 in absolute accuracy seems possible.

V. Tioukine, K. Aulenbacher, E. Riehn
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany

The European Physical Journal A 32, pp. 543–547 (2007)
Helicity correlated asymmetries caused by optical imperfections

received: 31 August 2006
published online: 14 June 2007

Abstract. False asymmetries in electron scattering experiments utilizing photoelectron sources are generated by imperfections of the light polarization optics. The false asymmetries are amplified by an analyzing power of the photocathodes. We have demonstrated compensation techniques which allow to approach zero intensity asymmetry with good stability. Even in the absence of analyzing powers fluctuations may be generated by more subtle effects like varying interference patterns of the exciting laser beam.

K. Aulenbacher (for the A4 Collaboration)
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany

Nuclear Instruments and Methods in Physics Research A 568, pp. 537–542 (2006)
Operation of the MAMI accelerator with a Wien filter based spin rotation system

received 7 October 2005
received in revised form 9 August 2006
accepted 10 August 2006
available online 5 September 2006

Abstract. A compact spin rotation system based on a Wien filter has been installed at the Mainz microtron accelerator (MAMI). Under operation with varying spin rotation angles a significant change of focal length together with a shift of the central beam trajectory is expected. We demonstrate that these effects can be kept under control. As a consequence operation with spin rotation angles between 0° and ± 90° has been achieved without compromising the beam quality and operational stability of MAMI.

V. Tioukine, K. Aulenbacher
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany

Nuclear Instruments and Methods in Physics Research A 534, pp. 361–370 (2004)
First attempt of the measurement of the beam polarization at an accelerator with the optical electron polarimeter POLO

received 1 June 2004
accepted 9 June 2004
available online 25 August 2004

Abstract. The conventional methods for measuring the polarization of electron beams are either time consuming, invasive or accurate only to a few percent. We developed a method to measure electron beam polarization by observing the light emitted by argon atoms following their excitation by the impact of polarized electrons. The degree of circular polarization of the emitted fluorescence is directly related to the electron polarization. We tested the polarimeter on a test GaAs source available at the MAMI electron accelerator in Mainz, Germany. The polarimeter determines the polarization of a 50 keV electron beam decelerated to a few eV and interacting with an effusive argon gas jet. The resulting decay of the excited states produces the emission of a circularly polarized radiation line at 811.5nm which is observed and analyzed.

B. Collin¹, J. Arianer¹, S. Essabaa¹, R. Frascaria¹, R. Gacougnolle¹, R. Kunne¹, K. Aulenbacher², V. Tioukine²
¹ Institut de Physique Nucleáire/IN2P3 91406 Orsay Cedex, France
² Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany

Journal of Applied Physics - Volume 92, Issue 12, pp. 7536-7543 (2002)
Pulse response of thin III/V semiconductor photocathodes

received 3 June 2002
accepted 20 September 2002

Abstract. The response time and spin relaxation time of thin unstrained and strained III/V-semiconductor photocathodes installed in sources of polarized electrons have been investigated. Cathodes of various active layer thicknesses have been studied. An upper limit for the response time of a 150 nm thick strained layer photocathode has been found to be 2.5 ps. As a consequence, the average depolarization during transport in the conduction band to the surface is estimated to be lower than 3% and does not contribute substantially to the upper limit of about 80% for the spin polarization of the emitted electrons. The results indicate a high surface recombination velocity of S>1.2⋅10⁷ cm/s at the surface band bending region.

K. Aulenbacher¹, J. Schuler¹, D. v. Harrach¹, E. Reichert², J. Röthgen¹, A. Subashev³, V. Tioukine¹, Y. Yashin³
¹ Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany
² Institut für Physik, Johannes-Gutenberg Universität Mainz, Staudingerweg-7, D-55099 Mainz, Germany
³ State Technical University, 195251 St. Petersburg, Russia

J. Phys.: Conf. Ser. 298 (2011)
High average photocurrent research at MAMI

Abstract. We have measured the extractable charge during one lifetime (Charge lifetime, Q_&tau) of a NEA-GaAs-photocathode for two beam diameters. A limitation of Q_&tau to 1100 Coulomb due to ion-back-bombardment was observed for a 1.5 mm diameter emission site. When increasing the laser diameter from .3 to 1.5 mm we observe an increase of Q_&tau by a factor ~ 5, which is in disagreement with the assumed proportionality of the charge lifetime with emission area. Possible reasons for this discrepancy are analyzed.

K. Aulenbacher¹, I. Alexander¹, V. Tioukine¹, E. Riehn¹,
(at the Workshop on Sources of Polarized Leptons and High Brightness Electron Beams (PESP 2010), Bonn, 21-24 Sept 2010)
¹ Institute of Nuclear Physics, Mainz University, Mainz, Germany

AIP Conf.Proc.1149 (2009)
Hydrogen cleaning of superlattice photocathodes

Abstract. Surface cleaning with a beam of thermally dissociated hydrogen atoms was applied to superlattice cathodes which resulted in a considerable improvement of quantum efficiency. Compared to untreated samples no significant reduction of polarization of the emitted electrons was observed.

K. Aulenbacher¹, V. Tioukine¹, E. Riehn¹,
(at the 18th International Spin Physics Symposium (SPIN 2008), Charlottesville, Virginia, 6-11 Oct 2008)
¹ Institute of Nuclear Physics, Mainz University, Mainz, Germany

AIP Conf.Proc.1149 (2009)
Ab initio calculation of effective sherman functions in MeV Mott scattering

Abstract. A Mott polarimeter operating at energies from 1 to 3.5 MeV and at backward scattering angle of 164 degree has been installed at the MAMI accelerator. Its detection system is based on magnetic spectrometers allowing for efficient background suppression. The useful range of primary currents is between 10 nA and 100 µA, hence adapted to the typical beam currents at MAMI. The reduction of analyzing power due to multiple scattering can be calculated directly from the cross sections with the help of Monte Carlo simulation.

K. Aulenbacher¹, V. Tioukine¹,
(at the 18th International Spin Physics Symposium (SPIN 2008), Charlottesville, Virginia, 6-11 Oct 2008)
¹ Institute of Nuclear Physics, Mainz University, Mainz, Germany

SLAC-PUB-12980 (2007)
Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice with Distributed Bragg Reflector

Abstract. Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strained superlattice structures is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by the order of magnitude in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these photocathodes for spinpolarized electron sources.

L. G. Gerchikov¹, K. Aulenbacher², J. E. Clendenin³, V. V. Kuz’michev¹, Yu. A. Mamaev¹, T. Maruyama³, V. S. Mikhrin⁴, J. S. Roberts⁵, V. M. Ustinov⁴, D. A. Vasiliev¹, Yu. P.Yashin¹, A. E. Zhukov⁴
(at the XIIth International Workshop "Polarized Sources, Targets & Polarimetry" (PSTP2007), 10.-14. 09. 2007, Brookhaven National Laboratory)
¹ St. Petersburg State Polytechnic University, Russia
² Institute of Nuclear Physics, Mainz University, Mainz, Germany
³ Stanford Linear Accelerator Center, Stanford, CA, USA
⁴ A.F. Ioffe Physicotechnical Institute RAS, Russia
⁵ Department of Electronic and Electrical Engineering, University of Sheffield, UK

AIP conference proceedings vol. 915, Melville, New York (2007)
Polarized electron source operation at average currents of several milliamperes

Editors: K. Imai, T. Murakami, N. Saito, K. Tanida
ISBN: 978-0-7354-0423-6

Abstract. The assumption of a constant charge per lifetime of NEA photocathodes was tested at polarized electron currents of several mA. Polarized electrons were produced from bulk GaAs photocathodes by laser illumination with a photon energy close to the band gap. We demonstrate that cathode heating, ion trapping and increased relative beam loss due to space charge effects may lead to reduction of charge lifetime. We also find that cathode lifetime increases by a factor four when we increase the photon energy to 2.3 eV.

R. Barday, K. Aulenbacher
(at the 17th international Spin Physics Symposium, 2.-7. 10. 2007, Kyoto, Japan)
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55118 Mainz, Germany

Proceedings PAVI2006: "From Parity Violation to Hadronic Structure and more..."
Helicity correlated asymmetries caused by optical imperfections

Editors: K. de Jager, S. Kox, D. Lhuillier, F. Maas, S. Page C.Papanicolas, S. Stiliaris, J. van de Wiele
ISBN: 10 3-540-74412-6; Springer (2007)

K. Aulenbacher
(at the 3rd International Workshop, 16.-20. 5. 2006, Milos Island, Griechenland)
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55118 Mainz, Germany
&rarr siehe auch: Eur. Phys. J. A 32 543-547 (2007)

Proceedings of 16th international Spin Physics Symposium
Summary of the Workshop on Spin Polarized Electron Sources and Polarimeters

Editors: K. Aulenbacher, F. Bradamante, A. Bessan, A. Martin
ISBN: 981-256-315-6

Abstract. This is a summary report concerning results reported within the contributions to the PESP-2004 workshop. Progress in cathode technology and basic understanding of photoemission processes was reviewed together with performance improvements for operating sources at accelerators. Important subsystems like polarimeters, lasers sources and high voltage design were also presented showing a variaty of improvements and innovations.

K. Aulenbacher
(at the 16th international Spin Physics Symposium, SPIN 2004, Trieste, 10.-16.10.2004, Trieste, Italien)
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55118 Mainz, Germany

Proceedings of 16th international Spin Physics Symposium
Photocathode life time research at MAMI

K. Aulenbacher, F. Bradamante, A. Bessan, A. Martin
ISBN: 981-256-315-6

Abstract. The degradiation of Photocathode quantum efficiency was studied under different experimental conditions at MAMI. We find that current induced effects become dominant at currents higher than 65 µA. At smaller currents the lifetime of the photocathode is limited to a few weeks by the vacuum conditions in operation. We intend to improve the situation by using extensive NEG coating. Further studies of source liftime under high average currents are presented.

K. Aulenbacher, G. Arz, R. Barday, V. Tioukine
(at the Workshop on Polarized Electron Sources and Polarimeters, PESP2004, Trieste, 7.-9.10.2004, Mainz, Deutschland)
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55118 Mainz, Germany

Proceedings of 16th international Spin Physics Symposium
Time resolved depolarization measurements on superlattices with strained wells

K. Aulenbacher, F. Bradamante, A. Bessan, A. Martin
ISBN: 981-256-315-6

Abstract. Strained layer superlattices of the InAlGaAs/AlGaAs Type were investigated. Conventional measurements of c.w.-Polarization and quantum efficiency show good polarization(≈80%) and high q.e. (>1%). Surprisingly the pulse response is rather slow. The polarizations at the beginning of the puilse response seem to approach or even exceed the value of 90%, whereas the average polarization of the response is reduced by almost 10%.

K. Aulenbacher¹, R. Bolenz¹, V. Tioukine¹, M. Weis¹, A. V. Subashev², Y. Yashin²
(at the Workshop on Polarized Electron Sources and Polarimeters, PESP2004, Trieste, 7.-9.10.2004, Mainz, Deutschland)
¹ Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany
² Sankt Petersburg State Polytechnical University, Polyteknicheskaya 29, 19251 St. Petersburg, Russia

AIP conference proceedings vol. 675 , Melville New York, p.1088-1092 (2003)
Status of the polarized source at MAMI

Editors: Y.I. Makdisi, A.U. Luccio, W.W. MacKay
ISBN: 0-7354-0136-5

Abstract. This talks addresses the operation of the polarized source at the Mainz Microtron MAMI. The source is operating with selected photocathodes of modulation doped, uniaxially strained layer photocathodes, which results in an average spin polarization of 80% and a quantum efficiency of typically 2µA/mW. The operative lifetime has been improved by employing a novel activation technique which reduces transmission losses in the vicinity of the cathode. In addition a considerable simplification of the laser system has become possible by improving the power output of laser diode seed lasers so that it is not necessary to employ power amplifier units. It was shown that the potential for increasing the laser power is limited in our setup because of the thermal resistance between cathode and the surrounding electrode.

K. Aulenbacher, V. Tioukine, M. Wiessner, K. Winkler
(at the 15th international Spin Physics symposium - Workshop Polarized electron sources, 4.-6. 9. 2002, Danvers, Massachusetts)
Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55118 Mainz, Germany

Proceedings of the 8th European accelerator conference, EPAC Paris (2002)
Spin manipulation at MAMI-C

p. 1816

Abstract. The construction of the fourth stage of the Mainz Microtron (MAMI-C) requires improvements of spinmanipulation techniques. A first goal is to provide 90 degrees spin rotation for all extraction energies of the Harmonic Double Sided Microtron (HDSM) which forms the fourth stage of MAMI (850-1500 MeV). This can be achieved by the presently applied energy variation technique if an additional accelerating section is installed in the interface between the accelerator stage RTM3 and the HDSM which is presently under construction. On the other hand, the need for spin manipulation at low energies e.g. for precision beam-polarimetry and for attaining out of plane polarization has led to a study for the introduction of a Wien-filter-system. The Wien filter is used at the injection energy of MAMI which is 100 keV. Operation of this very compact system with a quadrupole compensation has been demonstrated in a test stand. Promising results have been achieved for spin rotation angles as large as 60 degrees. Installation and operation of the filter for intermediate energy physics experiments is scheduled in the near future.

V. Tioukine¹, K. Aulenbacher¹, H. Euteneuer¹, K.H. Kaiser¹, S. Ratschow²
¹ Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany
² Darmstadt University of Technology

Proceedings of the 8th European accelerator conference, EPAC Paris (2002)
Development of an optical electron polarimeter with Argon gas

p. 1861

Abstract. The conventional methods for measuring the polarization of electron beams are time consuming, invasive and accurate only to a few percents. An optical method has been developed to measure electron beam polarization by observing the light emitted by argon atoms following their excitation by electron impact. It has been shown that the collision induces a spin transfer from the polarized electron to the argon atom, which decays by emitting a circularly polarized fluorescence. The degree of circular polarization is directly related to the electron polarization. Such a polarimeter is under test in Mainz, on a test GaAs source available at the IKP Mainz. It will determine the polarization of a 50keV electron beam decelerated to a few eV interacting with an effusive gas jet. Argon atoms are excited by electrons of approximately 20eV. The resulting decay of the excited states produces the emission of a circularly polarized radiation line at 811.5nm which is observed and analyzed. The excitation function of the 811.5nm radiation line has been studied as a function of the energy of the decelerated electrons. We are now investigating the measurement of the fluorescence polarization through its Stokes parameters by means of a Fast Fourier Transform (FFT) analysis.

B. Collin¹, J. Arianer¹, S. Essabaa¹, R. Frascaria¹, R. Gacougnolle¹, R. Kunne¹, K. Aulenbacher², V. Tioukine²
¹ Institut de Physique Nucleáire/IN2P3 91406 Orsay Cedex, France
² Institut für Kernphysik, Johannes-Gutenberg Universität Mainz, J.-J. Becherweg 45, D-55099 Mainz, Germany