Sijtze Brandenburg

EDEN - A NEUTRON TIME-OF-FLIGHT MULTIDETECTOR FOR DECAY STUDIES OF GIANT STATES

A neutron time-of-flight multidetector has been built to study the decay of giant states. It is made of 40 individual detectors. A liquid scintillator is used for neutron-gamma-ray pulse shape discrimination. The overall efficiency of the multidetector (epsilonOMEGA/4pi) is 1% for 6 MeV neutrons and the energy resolution is about 60 keV and 500 keV for 1 MeV and 6 MeV neutrons respectively.

Lung irradiation induces pulmonary vascular remodelling resembling pulmonary arterial hypertension

Background Pulmonary arterial hypertension (PAH) is a commonly fatal pulmonary vascular disease that is often diagnosed late and is characterised by a progressive rise in pulmonary vascular resistance resulting from typical vascular remodelling. Recent data suggest that vascular damage plays an important role in the development of radiation-induced pulmonary toxicity. Therefore, the authors investigated whether irradiation of the lung also induces pulmonary hypertension. Methods Different sub-volumes of the rat lung were irradiated with protons known to induce different levels of pulmonary vascular damage. Results Early loss of endothelial cells and vascular oedema were observed in the irradiation field and in shielded parts of the lung, even before the onset of clinical symptoms. 8 weeks after irradiation, irradiated volume-dependent vascular remodelling was observed, correlating perfectly with pulmonary artery pressure, right ventricle hypertrophy and pulmonary dysfunction. Conclusions The findings indicate that partial lung irradiation induces pulmonary vascular remodelling resulting from acute pulmonary endothelial cell loss and consequential pulmonary hypertension. Moreover, the close resemblance of the observed vascular remodelling with vascular lesions in PAH makes partial lung irradiation a promising new model for studying PAH.

A small-angle large-acceptance detection system for hadrons

Abstract The performance of a segmented large-acceptance detector, capable of measuring particles at small forward angles, is presented. The Small-Angle Large-Acceptance Detector (SALAD), was built to handle very high rates of particles impinging on the detector. Particles down to a few MeV can be detected with it. The position of charged particles is measured by two Multi-Wire Proportional Chambers while scintillator blocks are used to measure the energy of the detected particle. A stack of thin scintillators placed behind the energy detectors allows for a hardware rejection (veto) of high-energy particles going through the scintillator blocks.

Short-lived positron emitters in beam-on PET imaging during proton therapy

The only method for in vivo dose delivery verification in proton beam radiotherapy in clinical use today is positron emission tomography (PET) of the positron emitters produced in the patient during irradiation. PET imaging while the beam is on (so called beam-on PET) is an attractive option, providing the largest number of counts, the least biological washout and the fastest feedback. In this implementation, all nuclides, independent of their half-life, will contribute. As a first step towards assessing the relevance of short-lived nuclides (half-life shorter than that of (10)C, T1/2  =  19 s) for in vivo dose delivery verification using beam-on PET, we measured their production in the stopping of 55 MeV protons in water, carbon, phosphorus and calcium The most copiously produced short-lived nuclides and their production rates relative to the relevant long-lived nuclides are: (12)N (T1/2  =  11 ms) on carbon (9% of (11)C), (29)P (T1/2  =  4.1 s) on phosphorus (20% of (30)P) and (38m)K (T1/2  =  0.92 s) on calcium (113% of (38g)K). No short-lived nuclides are produced on oxygen. The number of decays integrated from the start of an irradiation as a function of time during the irradiation of PMMA and 4 tissue materials has been determined. For (carbon-rich) adipose tissue, (12)N dominates up to 70 s. On bone tissue, (12)N dominates over (15)O during the first 8-15 s (depending on carbon-to-oxygen ratio). The short-lived nuclides created on phosphorus and calcium provide 2.5 times more beam-on PET counts than the long-lived ones produced on these elements during a 70 s irradiation. From the estimated number of (12)N PET counts, we conclude that, for any tissue, (12)N PET imaging potentially provides equal to superior proton range information compared to prompt gamma imaging with an optimized knife-edge slit camera. The practical implementation of (12)N PET imaging is discussed.

Multipurpose superconducting electron cyclotron resonance ion source, the European roadmap to third-generation electron cyclotron resonance ion sources

The major infrastructures of nuclear physics in Europe adopted the technology of electron cyclotron resonance (ECR) ion sources for the production of heavy-ion beams. Most of them use 14GHz electron cyclotron resonance ion sources (ECRISs), except at INFN-LNS, where an 18GHz superconducting ECRIS is in operation. In the past five years it was demonstrated, in the frame of the EU-FP5 RTD project called “Innovative ECRIS,” that further enhancement of the performances requires a higher frequency (28GHz and above) and a higher magnetic field (above 2.2T) for the hexapolar field. Within the EU-FP6 a joint research activity named ISIBHI has been established to build by 2008 two different ion sources, the A-PHOENIX source at LPSC Grenoble, reported in another contribution, and the multipurpose superconducting ECRIS (MS-ECRIS), based on fully superconducting magnets, able to operate in High B mode at a frequency of 28GHz or higher. Such a development represents a significant step compared to existing devices, and...

γ-decay of the deeply-bound hole states in 101Pd, 105Pd, 107Pd, 111Sn, 117Sn observed in the (3He, αγ) reaction at 70 MeV

Abstract The γ-decay of deep-hole states in 101, 105, 107 Pd was studied via the ( 3 He, αγ) reaction at E 3 he = 70 MeV and supplemented by data from 112, 118 Sn targets to investigate the deep-hole spreading mechanism. The γ-decay pattern for the g 9 2 deep-hole state shows a strong dependence on the spreading width: if the deep-hole state is observed as a sharp peak, it mainly decays to the low-lying 7 2 + state by a spin-flip M1 transition with a large M1-E2 mixing ratio; if the deep-hole state is observed as a broad bump, it decays statistically indicating the complete spreading of the hole strength over the underlying states; if the deep-hole state is observed with a structure intermediate between a sharp peak and broad bump, its γ-decay shows both decay patterns. A sharp peak at E x = 2.396 MeV in 101 Pd which carries a large fraction of the g 9 2 hole strength ( C 2 S = 2.0) was found to be a single state having a width of less than 2.5 keV. For the spin-flip M1 transition the destructive interference between the g 9 2 component and the coupled components of the deep-hole state was found in heavily spread states. A quasiparticle-plus-rotor (QPR) model was applied to calculate the fragmentation in the doorway stage for the g 9 2 neutron deep-hole state in the Pd isotopes. A reasonable agreement between the calculation and the experimental results was obtained for the strength fragmentation, for the nucleus 101 Pd. However, the large M1-E2 mixing ratio experimentally observed was not reproduced.

Status report of the multipurpose superconducting electron cyclotron resonance ion source

Intense heavy ion beam production with electron cyclotron resonance (ECR) ion sources is a common requirement for many of the accelerators under construction in Europe and elsewhere. An average increase of about one order of magnitude per decade in the performance of ECR ion sources was obtained up to now since the time of pioneering experiment of R. Geller at CEA, Grenoble, and this trend is not deemed to get the saturation at least in the next decade, according to the increased availability of powerful magnets and microwave generators. Electron density above 10(13) cm(-3) and very high current of multiply charged ions are expected with the use of 28 GHz microwave heating and of an adequate plasma trap, with a B-minimum shape, according to the high B mode concept [S. Gammino and G. Ciavola, Plasma Sources Sci. Technol. 5, 19 (1996)]. The MS-ECRIS ion source has been designed following this concept and its construction is underway at GSI, Darmstadt. The project is the result of the cooperation of nine European institutions with the partial funding of EU through the sixth Framework Programme. The contribution of different institutions has permitted to build in 2006-2007 each component at high level of expertise. The description of the major components will be given in the following with a view on the planning of the assembly and commissioning phase to be carried out in fall 2007. An outline of the experiments to be done with the MS-ECRIS source in the next two years will be presented.

Low-lying octupole strength in 112Cd

The low-lying octupole strength distribution in 112Cd has been measured by means of inelastic proton scattering. A splitting of the strength has been observed and interpreted as due to the interaction between the quadrupole and octupole degrees of freedom. The splitting can be reproduced by the IBA-1 model if the coupling of f- and d-bosons is considered.

Fission decay of the isoscalar giant quadrupole resonance in 24Mg

Abstract The 24 Mg (α, α′) 12 C + 12 C reaction was studied by measuring 12C fragments in coincidence with inelastically scattered α-particles at Eα = 120 MeV. Both 12C fragments were identified using the ΔE − E technique. The measured angular correlations indicate that the 12Cgs+12Cgs decay channel is dominated by decay of L = 2 strength, which yields an integrated fraction of 0.14% of the E2 EWSR strength in comparison with 22.2% of the E2 EWSR strength observed in singles inelastic α-scattering experiments in the same excitation energy region.

Spectra of clinical CT scanners using a portable Compton spectrometer

PURPOSE Spectral information of the output of x-ray tubes in (dual source) computer tomography (CT) scanners can be used to improve the conversion of CT numbers to proton stopping power and can be used to advantage in CT scanner quality assurance. The purpose of this study is to design, validate, and apply a compact portable Compton spectrometer that was constructed to accurately measure x-ray spectra of CT scanners. METHODS In the design of the Compton spectrometer, the shielding materials were carefully chosen and positioned to reduce background by x-ray fluorescence from the materials used. The spectrum of Compton scattered x-rays alters from the original source spectrum due to various physical processes. Reconstruction of the original x-ray spectrum from the Compton scattered spectrum is based on Monte Carlo simulations of the processes involved. This reconstruction is validated by comparing directly and indirectly measured spectra of a mobile x-ray tube. The Compton spectrometer is assessed in a clinical setting by measuring x-ray spectra at various tube voltages of three different medical CT scanner x-ray tubes. RESULTS The directly and indirectly measured spectra are in good agreement (their ratio being 0.99) thereby validating the reconstruction method. The measured spectra of the medical CT scanners are consistent with theoretical spectra and spectra obtained from the x-ray tube manufacturer. CONCLUSIONS A Compton spectrometer has been successfully designed, constructed, validated, and applied in the measurement of x-ray spectra of CT scanners. These measurements show that our compact Compton spectrometer can be rapidly set-up using the alignment lasers of the CT scanner, thereby enabling its use in commissioning, troubleshooting, and, e.g., annual performance check-ups of CT scanners.