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S Roesler

Publications and source records attributed to S Roesler.

18 recordsLinked to original sources
PubMed2005

The FLUKA code: new developments and application to 1 GeV/n iron beams.

The modeling of ion transport and interactions in matter is a subject of growing interest, driven by the continuous increase of possible application fields. These include hadron therapy, dosimetry, and space missions, but there are also several issues involving fundamental research, accelerator physics, and cosmic ray physics, where a reliable description of heavy ion induced cascades is important. In the present work, the capabilities of the FLUKA code for ion beams will be briefly recalled and some recent developments presented. Applications of the code to the simulation of therapeutic carbon, nitrogen and oxygen ion beams, and of iron beams, which are of direct interest for space mission related experiments, will be also presented together with interesting consideration relative to the evaluation of dosimetric quantities. Both applications involve ion beams in the AGeV range.

Carbon↗
PubMed2005

Benchmark studies of induced radioactivity produced in LHC materials, Part I: Specific activities.

Samples of materials which will be used in the LHC machine for shielding and construction components were irradiated in the stray radiation field of the CERN-EU high-energy reference field facility. After irradiation, the specific activities induced in the various samples were analysed with a high-precision gamma spectrometer at various cooling times, allowing identification of isotopes with a wide range of half-lives. Furthermore, the irradiation experiment was simulated in detail with the FLUKA Monte Carlo code. A comparison of measured and calculated specific activities shows good agreement, supporting the use of FLUKA for estimating the level of induced activity in the LHC.

Benchmarking↗
PubMed2005

Benchmark studies of induced radioactivity produced in LHC materials, Part II: Remanent dose rates.

A new method to estimate remanent dose rates, to be used with the Monte Carlo code FLUKA, was benchmarked against measurements from an experiment that was performed at the CERN-EU high-energy reference field facility. An extensive collection of samples of different materials were placed downstream of, and laterally to, a copper target, intercepting a positively charged mixed hadron beam with a momentum of 120 GeV c(-1). Emphasis was put on the reduction of uncertainties by taking measures such as careful monitoring of the irradiation parameters, using different instruments to measure dose rates, adopting detailed elemental analyses of the irradiated materials and making detailed simulations of the irradiation experiment. The measured and calculated dose rates are in good agreement.

Benchmarking↗
PubMed2005

Remanent dose rates around the collimators of the LHC beam cleaning insertions.

The LHC will require an extremely powerful and unprecedented collimation system. As approximately 30% of the LHC beam is lost in the cleaning insertions, these will become some of the most radioactive locations around the entire LHC ring. Thus, remanent dose rates to be expected during later repair or maintenance interventions must be considered in the design phase itself. As a consequence, the beam cleaning insertions form a unique test bed for a recently developed approach to calculate remanent dose rates. A set of simulations, different in complexity, is used in order to evaluate methods for the estimation of remanent dose rates. The scope, as well as the restrictions, of the omega-factor method are shown and compared with the explicit simulation approach. The latter is then used to calculate remanent dose rates in the beam cleaning insertions. Furthermore, a detailed example for maintenance dose planning is given.

Computer Simulation↗
PubMed2005

Characterisation of ionisation chambers for a mixed radiation field and investigation of their suitability as radiation monitors for the LHC.

Monitoring of the radiation environment is one of the key tasks in operating a high-energy accelerator such as the Large Hadron Collider (LHC). The radiation fields consist of neutrons, charged hadrons as well as photons and electrons with energy spectra extending from those of thermal neutrons up to several hundreds of GeV. The requirements for measuring the dose equivalent in such a field are different from standard uses and it is thus necessary to investigate the response of monitoring devices thoroughly before the implementation of a monitoring system can be conducted. For the LHC, it is currently foreseen to install argon- and hydrogen-filled high-pressure ionisation chambers as radiation monitors of mixed fields. So far their response to these fields was poorly understood and, therefore, further investigation was necessary to prove that they can serve their function well enough. In this study, ionisation chambers of type IG5 (Centronic Ltd) were characterised by simulating their response functions by means of detailed FLUKA calculations as well as by calibration measurements for photons and neutrons at fixed energies. The latter results were used to obtain a better understanding and validation of the FLUKA simulations. Tests were also conducted at the CERF facility at CERN in order to compare the results with simulations of the response in a mixed radiation field. It is demonstrated that these detectors can be characterised sufficiently enough to serve their function as radiation monitors for the LHC.

Computer-Aided Design↗
PubMed2004

The FLUKA code for space applications: recent developments.

The FLUKA Monte Carlo transport code is widely used for fundamental research, radioprotection and dosimetry, hybrid nuclear energy system and cosmic ray calculations. The validity of its physical models has been benchmarked against a variety of experimental data over a wide range of energies, ranging from accelerator data to cosmic ray showers in the earth atmosphere. The code is presently undergoing several developments in order to better fit the needs of space applications. The generation of particle spectra according to up-to-date cosmic ray data as well as the effect of the solar and geomagnetic modulation have been implemented and already successfully applied to a variety of problems. The implementation of suitable models for heavy ion nuclear interactions has reached an operational stage. At medium/high energy FLUKA is using the DPMJET model. The major task of incorporating heavy ion interactions from a few GeV/n down to the threshold for inelastic collisions is also progressing and promising results have been obtained using a modified version of the RQMD-2.4 code. This interim solution is now fully operational, while waiting for the development of new models based on the FLUKA hadron-nucleus interaction code, a newly developed QMD code, and the implementation of the Boltzmann master equation theory for low energy ion interactions.

Computer Simulation↗
PubMed2004

[Transumbilical laparoscopic-assisted "one-trocar" appendectomy -- TULAA -- as an alternative operation method in the treatment of appendicitis].

INTRODUCTION: Appendectomy is one of the most commonly performed surgical procedures in general surgery and laparoscopic appendectomy represents the beginning of minimal invasive era in visceral surgery. But until yet, laparoscopic appendectomy is not the standard method for removal of the appendix and the discussion about the value and the advantages of laparoscopic appendectomy is still going on between the opponents and advocates of this method. In this article we present the transumbilical laparoscopic assisted "one-trocar" appendectomy (TULAA) as an alternative procedure for appendectomy and our experiences with this technique, which is up to now not very well known in Germany. METHOD: From November 1, 2000 to December 31, 2002, we performed appendectomy in 350 patients. 163 patients (46.6 %) underwent TULAA in the technique of Begin. All of them were examined two weeks and three months after surgery. RESULTS: In 94.5 % the "one-trocar" appendectomy was successful and there were no intraoperative complications. The mortality was 0 %. Conversion to the open procedure was necessary in 3 patients (1.8 %), respectively introduction of accessory trocars was necessary in 6 patients (3.7 %). In 111 from 163 patients (68.1 %) appendectomy was performed because of acute appendicitis. In 14.1 % we detected additional secondary findings during the laparoscopy. The postoperative complication rate was 3.6 %. CONCLUSION: The transumbilical laparoscopic assisted "one-trocar" appendectomy complements the minimal invasive procedures in visceral surgery. The operating technique combines the simplicity and the safety of conventional appendectomy with the survey of laparoscopic appendectomy. It minimizes the trauma of surgery and shows a perfect cosmetic result.

Acute Disease↗
PubMed2004

Averaged particle dose conversion coefficients in air crew dosimetry.

The MCNPX Monte Carlo code was used to calculate energy-dependent fluence-to-effective dose conversion coefficients for neutrons, protons, electrons, photons, charged pions and muons. The FLUKA Monte Carlo code was used to calculate the spectral particle fluences of secondary cosmic rays for different altitudes, and for different combinations of solar modulation and vertical cut-off rigidity parameters. The energy-averaged fluence-to-dose conversion coefficients were obtained by folding the particle fluence spectra with the conversion coefficients for effective dose and ambient dose equivalent. They show a slight dependence on altitude, solar activity and location in the geomagnetic field.

Aircraft↗
PubMed2002

[Primary and secondary aortoiliac reconstructions in patients with coexistent horseshoe and pelvic kidney].

The coexistence of dystopic kidney and abdominal aortic aneurysm or aortoiliac occlusive arterial disease is uncommon (0.12-0.15 %) and constitutes a technical challenge to vascular surgeons. Between 1997 and 1999 we performed 249 aortoiliac reconstructions and encountered four patients (1.6 %) with dystopic kidneys. The aortoiliac reconstructions were performed successfully in all patients while maintaining renal blood supply. Aortoiliac reconstructions in patients with horseshoe or pelvic kidney show similar results as regular reconstructions on the condition that optimal preoperative diagnosis and operative technique are used considering atypical renal vessels. Nevertheless, pelvic kidneys can lead to serious complications as we describe in this report. On the basis of our patients anatomy, embryology and surgical management of this entity.

Aged↗
PubMed2002

Monte Carlo calculation of the radiation field at aircraft altitudes.

Energy spectra of secondary cosmic rays are calculated for aircraft altitudes and a discrete set of solar modulation parameters and rigidity cut-off values covering all possible conditions. The calculations are based on the Monte Carlo code FLUKA and on the most recent information on the interstellar cosmic ray flux including a detailed model of solar modulation. Results are compared to a large variety of experimental data obtained on the ground and aboard aircraft and balloons, such as neutron, proton, and muon spectra and yields of charged particles. Furthermore, particle fluence is converted into ambient dose equivalent and effective dose and the dependence of these quantities on height above sea level, solar modulation, and geographical location is studied. Finally, calculated dose equivalent is compared to results of comprehensive measurements performed aboard aircraft.

Aircraft↗
PubMed2000

[Effect of preoperative preoperative visualization therapy on postoperative outcome after inguinal hernia surgery and thyroid resection].

UNLABELLED: This randomized controlled trial aims to evaluate the influence of preoperative relaxation techniques on postoperative outcomes. From January 1997 to June 1998 208 patients were operated on for primary inguinal hernia or goiter. The patients were randomized into two groups: Group A (n = 103) underwent the surgical treatment with a preoperative visualization therapy. Group B (n = 105) underwent the surgical treatment without a preoperative therapy. Patients with age under 18 years, ASA-status IV-V, recurrent inguinal hernia or recurrent goiter and malignant neoplasms were excluded from the study. There were no differences in age, sex, duration of the operation, training of the surgeon, and preoperative blood parameters between the two groups. RESULTS: During the postoperative follow-up we observed more hematomas (group A with visualization therapy: 30.3%, group B without visualization therapy: 44.4%) as well as more pain (group A: 4.2, group B: 5.2) and analgesic consumption (group A: 59.7 mg Tramadol HCL, group B: 72.5 mg Tramadol HCL) in group B (p < 0.05). There were no significant differences in infections, nausea, hypocalcemia, tetania, recurrent nerve palsy, fever. CONCLUSIONS: Preoperative visualization therapy reduces significantly the number of postoperative hematomas after inguinal hernia repair. Furthermore a decrease of analgesic requirements after surgical treatment was observed.

Adult↗
PubMed1999

Cosmic rays and dosimetry at aviation altitudes.

Recent concerns regarding the effects of the cosmic radiation field at aircraft altitudes on aircrew have resulted in a renewed interest in detailed measurements of the neutral and charged particle components in the atmosphere. CR-39 nuclear track detectors have been employed on a number of subsonic and supersonic aircraft to measure charge spectra and LET spectra at aircraft altitudes. These detectors are ideal for long term exposures required for these studies and their passive nature makes them suitable for an environment where interference with flight instrumentation could be a problem. We report here on measurements and analysis of short range tracks which were produced by high LET particles generated mainly by neutron interactions at aviation altitudes. In order to test the overall validity of the technique measurements were also carried out at the CERN-CEC field which simulates the radiation field at aviation altitudes and good agreement was found with dose values obtained using mainly heavy ion calibration.

Aircraft↗
PubMed1999

Physics of cosmic radiation fields.

This paper glances at the knowledge of composition and energy spectra of galactic cosmic rays and briefly discusses the mechanism of solar modulation and of shielding against these particles by the earth's magnetic field. A short review of the properties of solar particle events is given, in which particles emitted from the sun enter the atmosphere. Particle production in the earth's atmosphere in hadronic and electromagnetic cascades is described and the altitude variations of the different particle components are investigated. Typical energy spectra in the atmosphere are presented for some types of particles.

Altitude↗
PubMed1998

Neutron spectra in the atmosphere from interactions of primary cosmic rays.

Spectra of neutrons from interactions of primary cosmic rays in the earth's atmosphere are calculated with the Monte Carlo model FLUKA for various depths down to sea level. We discuss the environmental models describing the primary cosmic ray spectrum and details of the calculations. Neutron energy spectra are presented for different depths in the atmosphere and for different geographical locations. By comparing results of calculations to measurements on neutron spectra it is shown that FLUKA may serve as an important tool for the estimation of the radiation environment in the atmosphere.

Atmosphere↗
PubMed1998

Neutron spectra at flight altitudes and their radiological estimation.

Since the publication of the ICRP-report 60, air crews and other frequently flying persons are considered as occupationally exposed people. At civil flight levels neutrons contribute the major part to the radiologically relevant dose to men. The quantification of the neutron dose, and herewith the radiation risk due to neutrons, suffers from spectral data available especially in the energy range above 20 MeV. Experimental data were recently obtained at a low flight level on top of the mountain Zugspitze at 3000m using a modified Bonner sphere spectrometer. The resulting spectra are compared with Monte-Carlo transport calculations from top of the atmosphere down to 700 g/cm2. These data and others from the literature are used to calculate operational and risk related quantities, i.e. ambient dose equivalent and effective dose.

Aerospace Medicine↗
PubMed1998

Calculation of radiation fields in the atmosphere and comparison to experimental data.

In this paper the spectra of secondary hadrons are determined in the atmosphere at various depths down to sea level. The calculations are performed using the Monte Carlo code FLUKA together with cosmic-ray environmental models which describe the spectra of primary cosmic-ray particles. We discuss the details of the calculations and the dependence of the results on the primary cosmic-ray spectrum, the atmospheric depth and the geographical location. Special emphasis is put on comparisons of calculated and measured hadron spectra including an experiment which was recently performed at the mountain Zugspitze (47.4 degrees N, 11.0 degrees E, 2963 m), Germany. It is shown that FLUKA may serve as an important tool for the estimation of the radiation environment in the atmosphere.

Cosmic Radiation↗