M. Holzscheiter - Academia.edu (original) (raw)

Papers by M. Holzscheiter

A small decelerator ring with electron cooling is proposed to produce dense antiproton beams at v... more A small decelerator ring with electron cooling is proposed to produce dense antiproton beams at very low energies. The ring should be installed between the existing AD and the experimental area

Astroparticle Physics, 2004

Several proposed source models for Ultra-High Energy Cosmic Rays (UHECRs) consist of dipole distr... more Several proposed source models for Ultra-High Energy Cosmic Rays (UHECRs) consist of dipole distributions oriented towards major astrophysical landmarks such as the galactic center, M87, or Centaurus A. We use a comparison between real data and simulated data to show that the HiRes-I monocular data for energies above 10 18.5 eV is, in fact, consistent with an isotropic source model. We then explore methods to quantify our sensitivity to dipole source models oriented towards the Galactic Center, M87, and Centaurus A.

Acta Oncologica, 2010

To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in ... more To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in vitro experiments at the TRIGA Mark II reactor at the University of Mainz, Germany, it is necessary to have a reliable dose monitoring system. The in vitro experiments are used to determine the relative biological effectiveness (RBE) of liver and cancer cells in our mixed neutron and gamma fi eld. We work with alanine detectors in combination with Monte Carlo simulations, where we can measure and characterize the dose. To verify our calculations we perform neutron fl ux measurements using gold foil activation and pin-diodes. Material and methods. When L-α-alanine is irradiated with ionizing radiation, it forms a stable radical which can be detected by electron spin resonance (ESR) spectroscopy. The value of the ESR signal correlates to the amount of absorbed dose. The dose for each pellet is calculated using FLUKA, a multipurpose Monte Carlo transport code. The pin-diode is augmented by a lithium fl uoride foil. This foil converts the neutrons into alpha and tritium particles which are products of the 7 Li(n, α) 3 H-reaction. These particles are detected by the diode and their amount correlates to the neutron fl uence directly. Results and discussion. Gold foil activation and the pin-diode are reliable fl uence measurement systems for the TRIGA reactor, Mainz. Alanine dosimetry of the photon fi eld and charged particle fi eld from secondary reactions can in principle be carried out in combination with MC-calculations for mixed radiation fi elds and the Hansen & Olsen alanine detector response model. With the acquired data about the background dose and charged particle spectrum, and with the acquired information of the neutron fl ux, we are capable of calculating the dose to the tissue. Conclusion. Monte Carlo simulation of the mixed neutron and gamma fi eld of the TRIGA Mainz is possible in order to characterize the neutron behavior in the thermal column. Currently we also speculate on sensitizing alanine to thermal neutrons by adding boron compounds.

Radiotherapy and Oncology, 2010

Background and purpose: Antiprotons have been suggested as a possibly superior modality for radio... more Background and purpose: Antiprotons have been suggested as a possibly superior modality for radiotherapy, due to the energy released when antiprotons annihilate, which enhances the Bragg peak and introduces a high-LET component to the dose. However, concerns are expressed about the inferior lateral dose distribution caused by the annihilation products. Methods: We use the Monte Carlo code FLUKA to generate depth-dose kernels for protons, antiprotons, and carbon ions. Using these we then build virtual treatment plans optimized according to ICRU recommendations for the different beam modalities, which then are recalculated with FLUKA. Dose-volume histograms generated from these plans can be used to compare the different irradiations. Results: The enhancement in physical and possibly biological dose from annihilating antiprotons can significantly lower the dose in the entrance channel; but only at the expense of a diffuse low dose background from long-range secondary particles. Lateral dose distributions are improved using active beam delivery methods, instead of flat fields. Conclusions: Dose-volume histograms for different treatment scenarios show that antiprotons have the potential to reduce the volume of normal tissue receiving medium to high dose, however, in the low dose region antiprotons are inferior to both protons and carbon ions. This limits the potential usage to situations where dose to normal tissue must be reduced as much as possible.

Radiotherapy and Oncology, 2012

Background: Radiotherapy with Antiprotons is currently investigated by the AD-4/ACE collaboration... more Background: Radiotherapy with Antiprotons is currently investigated by the AD-4/ACE collaboration. The hypothesis is that the additional energy released from the antiprotons annihilating at the target nuclei can enable a reduced dose in the entry channel of the primary beam. Furthermore an enhanced[for full text, please go to the a.m. URL]

In this report the author describes the current status of the antiproton deceleration (AD) facili... more In this report the author describes the current status of the antiproton deceleration (AD) facility at CERN, and highlights the physics program with ultra-low energy antiproton at this installation. He also comments on future possibilities provided higher intensity antiproton beams become available at Fermilab, and review possibilities for initial experiments using direct degrading of high energy antiprotons in material has been developed and proven at CERN.

AIP Conference Proceedings, 1991

Ideas are presented for an experiment to compare the acceleration, g, of antiprotons in the Earth... more Ideas are presented for an experiment to compare the acceleration, g, of antiprotons in the Earth&amp;amp;amp;amp;amp;amp;amp;#39;s gravitational field with that of particles of normed matter, such as protons or hydrogen ions. The experiments will test whether antiprotons obey the weak equivalence principle.(AIP)

Lecture Notes in Computer Science, 1999

We briefly review the development and theory of an experiment to investigate quantum computation ... more We briefly review the development and theory of an experiment to investigate quantum computation with trapped calcium ions. The ion trap, laser and ion requirements are determined, and the parameters required for simple quantum logic operations are described.

31st Joint Propulsion Conference and Exhibit, 1995

Lecture Notes in Physics, 2001

Proceedings of the 2005 Particle Accelerator Conference, 2005

When completed, the DARHT-II linear induction accelerator (LIA) will produce a 2 kA, 18 MeV elect... more When completed, the DARHT-II linear induction accelerator (LIA) will produce a 2 kA, 18 MeV electron beam with more than 1500 ns current/energy "flat-top." In initial tests DARHT-II has already accelerated beams with current pulse lengths from 500 ns to 1200 ns full-width at half maximum (FWHM) with more than 1.2 kA peak current and 12.5 MeV peak energy. Experiments will soon begin with a ~1600 ns flat-top pulse, but with reduced current and energy. These pulse lengths are all significantly longer than any other multi-MeV LIA, and they define a novel regime for high-current beam dynamics, especially with regard to beam stability. Although the initial tests demonstrated the robustness of the DARHT-II LIA to BBU, the < 1200 ns FWHM pulse lengths were too short to test the predicted protection against ion-hose instability. The present experiments are designed to resolve these and other beam-dynamics issues with a ~1600 ns pulse length beam.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003

The second axis of the Dual Axis Radiographic Hydro-Test (DARHT) facility will provide up to four... more The second axis of the Dual Axis Radiographic Hydro-Test (DARHT) facility will provide up to four short (< 150 ns) radiation pulses for flash radiography of highexplosive driven implosion experiments[1]. To accomplish this the DARHT-II linear induction accelerator (LIA) will produce a 2-kA electron beam with 18-MeV kinetic energy, constant to within ± 0.5% for 2µs. A fast kicker will cleave four short pulses out of the 2µs flattop, with the bulk of the beam diverted into a dump. The short pulses will then be transported to the final-focus magnet, and focused onto a tantalum target for conversion to bremsstrahlung pulses for radiography. DARHT-II is a collaborative effort between the Los Alamos, Lawrence

Scientific Reports, 2013

Biological validation of new radiotherapy modalities is essential to understand their therapeutic... more Biological validation of new radiotherapy modalities is essential to understand their therapeutic potential. Antiprotons have been proposed for cancer therapy due to enhanced dose deposition provided by antiproton-nucleon annihilation. We assessed cellular DNA damage and relative biological effectiveness (RBE) of a clinically relevant antiproton beam. Despite a modest LET (,19 keV/mm), antiproton spread out Bragg peak (SOBP) irradiation caused significant residual c-H2AX foci compared to X-ray, proton and antiproton plateau irradiation. RBE of ,1.48 in the SOBP and ,1 in the plateau were measured and used for a qualitative effective dose curve comparison with proton and carbon-ions. Foci in the antiproton SOBP were larger and more structured compared to X-rays, protons and carbon-ions. This is likely due to overlapping particle tracks near the annihilation vertex, creating spatially correlated DNA lesions. No biological effects were observed at 28-42 mm away from the primary beam suggesting minimal risk from long-range secondary particles.

33rd Joint Propulsion Conference and Exhibit, 1997

... (1997), &amp;amp;quot;Antiproton-Catalyzed Microfission/Fusion Space Propulsion Syste... more ... (1997), &amp;amp;quot;Antiproton-Catalyzed Microfission/Fusion Space Propulsion Systems for Exploration of the Outer Solar System and Beyond,&amp;amp;quot; Space Technology and Applications International Forum (STAIF 97) January 26-30, 1997, Albuquerque, New Mexico, CONF-970115, ed. M. El ...

Physical Review Letters, 1991

Comment on "Does Antimatter Fall with the Same Acceleration as Ordinary Matter?" In a recent Lett... more Comment on "Does Antimatter Fall with the Same Acceleration as Ordinary Matter?" In a recent Letter [1], Adelberger et al. have shown that "equivalence-principle experiments with ordinary matter probe the gravivector acceleration of antimatter in the same way as do direct measurements of antimatter in free fall and set stringent upper limits on the gravivector acceleration of antimatter. " I subscribe to this conclusion for electrically neutral antimatter (e.g. , antihydrogen), but I wish to note that for the free fall of charged particles the formula E=(mg+q, V)e for the gravitational electric field used by Adelberger et al. [1] [their Eq. (3)]