No abstract

\textit{Objective}. Beams of stable ions have been a well-established tool for radiotherapy for many decades. In the case of ion beam therapy with stable $^{12}$C ions, the positron emitters $^{10,11}$C are produced via projectile and target fragmentation, and their decays enable visualization of the beam via positron emission tomography (PET). However, the PET activity peak matches the Bragg peak only roughly and PET counting statistics is low. These issues can be mitigated by using a short-lived positron emitter as a therapeutic beam. \textit{Approach.} An experiment studying the precision of the measurement of ranges of positron emitting carbon isotopes by means of PET has been performed at the FRS fragment-separator facility of GSI Helmholtzzentrum f"ur Schwerionenforschung GmbH, Germany. The PET scanner used in the experiment is a dual-panel version of a Siemens Biograph mCT PET scanner. \textit{Main results.} High quality in-beam PET images and activity distributions have been measured from the in-flight produced positron emitting isotopes $^{11}$C and $^{10}$C implanted into homogeneous PMMA phantoms. Taking advantage of the high statistics obtained in this experiment, we investigated the time evolution of the uncertainty of the range determined by means of PET during the course of an irradiation, and show that the uncertainty improves with the inverse square root of the number of PET counts. The uncertainty is thus fully determined by the PET counting statistics. During the delivery of 1.6$\times$10$^7$ ions in 4 spills for a total duration of 19.2~s, the PET activity range uncertainty for $^{10}$C, $^{11}$C and $^{12}$C is 0.04, 0.7 and 1.3~mm, respectively. The gain in precision related to the PET counting statistics is thus much larger when going from $^{11}$C to $^{10}$C than when going from $^{12}$C to $^{11}$C. The much better precision for $^{10}$C is due to its much shorter half-life, which, contrary to the case of $^{11}$C, also enables to include the in-spill data in the image formation. \textit{Significance}. Our results can be used to estimate the contribution from PET counting statistics to the precision of range determination in a particular carbon therapy situation, taking into account the irradiation scenario, the required dose and the PET scanner characteristics.

The proton-unbound argon and chlorine isotopes have been studied by measuring trajectories of their decay-in-flight products by using a tracking technique with micro-strip detectors. The proton (1p) and two-proton (2p) emission processes have been detected in the measured angular correlations "heavy-fragment"+p and "heavy-fragment"+p+p, respectively. The ground states of the previously unknown isotopes 30 Cl and 28 Cl have been observed for the first time, providing the 1p separation energies Sp of −0.48(2) and −1.60(8) MeV, respectively. The relevant systematics of 1p and 2p separation energies have been studied theoretically in the core+p and core+p+p cluster models. The first-time observed excited states of 31 Ar allow to infer the 2p-separation energy S2p of 6(34) keV for its ground state. The first-time observed state in 29 Ar with S2p = −5.50(18) MeV can be identified either as a ground or an excited state according to different systematics. * D.Kostyleva@gsi.de ary states in many theoretical applications. This naturally leads us to the question: what are the limits of nuclear structure existence? In other words, how far beyond the driplines the nuclear structure phenomena fade and are completely replaced by the continuum dynamics? This question represents a motivation for studies of nuclear systems far beyond the driplines.The proton and neutron driplines have been accessed for nuclides in broad ranges of Z (number of protons) and N (number of neutrons) of the nuclear chart. However, even in these regions the information about the nearest to the dripline unbound isotopes is scarce and often miss-

Several techniques are under development for image-guidance in particle therapy. Positron (β+) emission tomography (PET) is in use since many years, because accelerated ions generate positron-emitting isotopes by nuclear fragmentation in the human body. In heavy ion therapy, a major part of the PET signals is produced by β+-emitters generated via projectile fragmentation. A much higher intensity for the PET signal can be obtained using β+-radioactive beams directly for treatment. This idea has always been hampered by the low intensity of the secondary beams, produced by fragmentation of the primary, stable beams. With the intensity upgrade of the SIS-18 synchrotron and the isotopic separation with the fragment separator FRS in the FAIR-phase-0 in Darmstadt, it is now possible to reach radioactive ion beams with sufficient intensity to treat a tumor in small animals. This was the motivation of the BARB (Biomedical Applications of Radioactive ion Beams) experiment that is ongoing at GSI in Darmstadt. This paper will present the plans and instruments developed by the BARB collaboration for testing the use of radioactive beams in cancer therapy.

Mass measurements of As, Se, and Br nuclei, and their implication on the proton-neutron interaction strength toward the N = Z line

Prospects of experimental studies of argon and chlorine isotopes located far beyond the proton dripline are studied by using systematics and cluster models. The deviations from the widespread systematics observed in 28,29 Cl and 29,30 Ar have been theoretically substantiated, and analogous deviations predicted for the lighter chlorine and argon isotopes. The limits of nuclear structure existence are predicted for Ar and Cl isotopic chains, with 26 Ar and 25 Cl found to be the lightest sufficiently long-living nuclear systems. By simultaneous measurements of protons and γ-rays following decays of such systems as well as their β-delayed emission, an interesting synergy effect may be achieved, which is demonstrated by the example of 30 Cl and 31 Ar ground state studies. Such synergy effect may be provided by the new EXPERT setup (EXotic Particle Emission and Radioactivity by Tracking), being operated inside the fragment separator and spectrometer facility at GSI, Darmstadt.

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The full-size prototypes of large-area silicon detectors for the Time-Of-Flight (TOF) diagnostics of heavy ions were tested with 132Xe (600 MeV/u) beam. The obtained time resolution of the prototypes was about 13 ps, which satisfied the requirements of diagnostics for the Super Fragment Separator (Super-FRS) that is under development at GSI, Darmstadt, Germany. The irradiation effect on the timing properties of silicon detectors was studied with super-fast silicon pad detectors with a rise time of 190 ps. It was shown that the changes in the rise time of the leading edge of the detector current response to 40Ar ions (40.5 MeV/u) were negligible up to the fluence of 2 × 1011 ion/cm2 expected after one year of Super-FRS operation. This result confirms the model of the leading edge current pulse formation via a flow of the polarization current in dense tracks of heavy ions and shows the perspectives for application of silicon detectors for the TOF diagnostics of intensive heavy-ion beams.