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Fritz Caspers

Publications and source records attributed to Fritz Caspers.

13 recordsLinked to original sources
arXiv2022

Millimeter-wave WISP search with coherent Light-Shining-Through-a-Wall towards the STAX project

A dark photon is one of the simplest extensions of the Standard Model of particle physics and can be a dark matter candidate. Dark photons kinetically mix with ordinary photons. The mass range from $10^{-4}$ to $10^{-3}$ eV of such dark photons is under-constrained by laboratory-based experiments and a new search is therefore motivated. In this mass range, dark photons behave like waves rather than particles and the corresponding electromagnetic waves are in the millimeter-wave range. The technical difficulties of the millimeter waves have prevented so far dark photon experiments in this mass range. We propose the use of coherent millimeter waves to search for dark photons in a Light-Shining-through-a-Wall (LSW) experiment. We clarify the merit and limitations of coherent wave detection and briefly investigate the potential of single photon sensors at microwaves. Development of millimeter-wave technology is not only limited to dark photons. Technically, an experiment for dark photons by using electromagnetic waves resembles that for axions, another light dark matter candidate, with static magnetic fields. This paper represents an essential step towards axion LSW in the millimeter-wave range (STAX experiment) as a potential successor of an on-going experiment in infrared.

hep-ph↗
arXiv2020

First Results from Axion Haloscope at CAPP around 10.7 $\mu$eV

The Center for Axion and Precision Physics research at the Institute for Basic Science is searching for axion dark matter using ultra-low temperature microwave resonators. We report the exclusion of the axion mass range 10.7126$-$10.7186 $\mu$eV with near Kim-Shifman-Vainshtein-Zakharov (KSVZ) coupling sensitivity and the range 10.16$-$11.37 $\mu$eV with about 9 times larger coupling at 90$\%$ confidence level. This is the first axion search result in these ranges. It is also the first with a resonator physical temperature of less than 40 mK.

hep-ex↗
arXiv2015

Unconventional Ideas for Axion and Dark Matter Experiments

In this contribution an entirely different way compared to conventional approaches for axion, hidden photon and dark matter (DM) detection is proposed for discussion. The idea is to use living plants which are known to be very sensitive to all kind of environmental parameters, as detectors. A possible observable in such living plants could be the natural bio-photon level, a kind of metabolism related chemoluminescence. Another observable might be morphological changes or systematic leave movements. However a big problem for such kind of experiment would be the availability of a known, controllable and calibrated DM source. The objective of this small paper is primarily to trigger a debate and not so much to present a well-defined and clearly structured proposal.

hep-ex↗
arXiv2013

Microwave spectroscopic study of the hyperfine structure of antiprotonic helium-3

In this work we describe the latest results for the measurements of the hyperfine structure of antiprotonic helium-3. Two out of four measurable super-super-hyperfine SSHF transition lines of the (n,L)=(36,34) state of antiprotonic helium-3 were observed. The measured frequencies of the individual transitions are 11.12548(08) GHz and 11.15793(13) GHz, with an increased precision of about 43% and 25% respectively compared to our first measurements with antiprotonic helium-3 [S. Friedreich et al., Phys. Lett. B 700 (2011) 1--6]. They are less than 0.5 MHz higher with respect to the most recent theoretical values, still within their estimated errors. Although the experimental uncertainty for the difference of 0.03245(15) GHz between these frequencies is large as compared to that of theory, its measured value also agrees with theoretical calculations. The rates for collisions between antiprotonic helium and helium atoms have been assessed through comparison with simulations, resulting in an elastic collision rate of gamma_e = 3.41 +- 0.62 MHz and an inelastic collision rate of gamma_i = 0.51 +- 0.07 MHz.

physics.atom-ph↗
arXiv2012

LARP LHC 4.8 GHZ Schottky System Initial Commissioning with Beam

The LHC Schottky system consists for four independent 4.8 GHz triple down conversion receivers with associated data acquisition systems. Each system is capable of measuring tune, chromaticity, momentum spread in either horizontal or vertical planes; two systems per beam. The hardware commissioning has taken place from spring through fall of 2010. With nominal bunch beam currents of 1011 protons, the first incoherent Schottky signals were detected and analyzed. This paper will report on these initial commissioning results. A companion paper will report on the data analysis curve fitting and remote control user interface of the system.

physics.acc-ph↗
arXiv2012

Evaluation of the Beam Coupling Impedance of New Beam Screen Designs for the LHC Injection Kicker Magnets

During the 2011 run of the LHC there was a significant measured temperature increase in the LHC Injection Kicker Magnets (MKI) during operation with 50ns bunch spacing. This was due to increased beam-induced heating of the magnet due to beam impedance. Due to concerns about future heating with the increased total intensity to nominal and ultimate luminosities a review of the impedance reduction techniques within the magnet was required. A number of new beam screen designs are proposed and their impedance evaluated. Heating estimates are also given with a particular attention paid to future intensity upgrades to ultimate parameters.

physics.acc-ph↗
arXiv2012

Beam Coupling Impedance of the LHC TCTP Collimators

As part of an upgrade to the LHC collimation system, 8 TCTP and 1 TCSG collimators are proposed to replace existing collimators in the collimation system. In an effort to review all equipment placed in the accelerator complex for potential side effects due to collective effects and beam-equipment interactions, beam coupling impedance simulations are carried out in both the time-domain and frequency-domain of the full TCTP design. Particular attention is paid to trapped modes that may induce beam instabilities and beam-induced heating due to cavity modes of the device.

physics.acc-ph↗
arXiv2011

Simulations of Coaxial Wire Measurements of the Impedance of Asymmetric Structures

Coaxial wire measurements have provided a simple and effective way to measure the beam coupling impedance of accelerator structures for a number of years. It has been known how to measure the longitudinal and dipolar transverse impedance using one and two wires for some time. Recently the ability to measure the quadrupolar impedance of structures exhibiting top/bottom and left/right symmetry has been demonstrated. A method for measuring the beam coupling impedance of asymmetric structures using displaced single wires and two wire measurements is proposed. Simulations of the measurement system are presented with further work proposed.

physics.acc-ph↗
arXiv2011

Coaxial Wire Measurements of Ferrite Kicker Magnets

Fast kicker magnets are used to inject beam into and eject beam out of the CERN accelerator rings. These kickers are generally transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the yoke can provoke significant beam induced heating, especially for high intensities. In addition the impedance may contribute to beam instabilities. The results of longitudinal and transverse impedance measurements, for various kicker magnets, are presented and compared with analytical calculations: in addition predictions from a numerical analysis are discussed.

physics.acc-ph↗
arXiv2011

Comparison of the current LHC Collimators and the SLAC Phase 2 Collimator Impedances

One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design.

physics.acc-ph↗
arXiv2011

Prospects for Searching Axion-like Particle Dark Matter with Dipole, Toroidal and Wiggler Magnets

In this work we consider searches for dark matter made of axions or axion-like particles (ALPs) using resonant radio frequency cavities inserted into dipole magnets from particle accelerators, wiggler magnets developed for accelerator based advanced light sources, and toroidal magnets similar to those used in particle physics detectors. We investigate the expected sensitivity of such ALP dark matter detectors and discuss the engineering aspects of building and tuning them. Brief mention is also made of even stronger field magnets that are becoming available due to improvements in magnetic technology. It is concluded that new experiments utilizing already existing magnets could greatly enlarge the mass region in searches for axion-like dark matter particles.

physics.ins-det↗
arXiv2008

Beam Coupling Impedance Measurement and Mitigation for a TOTEM Roman Pot

The longitudinal and transverse beam coupling impedance of the first final TOTEM Roman Pot unit has been measured in the laboratory with the wire method. For the evaluation of transverse impedance the wire position has been kept constant, and the insertions of the RP were moved asymmetrically. With the original configuration of the RP, resonances with fairly high Q values were observed. In order to mitigate this problem, RF-absorbing ferrite plates were mounted in appropriate locations. As a result, all resonances were sufficiently damped to meet the stringent LHC beam coupling impedance requirements.

physics.ins-det↗