Coulomb dissociation of N 20,21

Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N20,21 are reported. Relativistic N20,21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the N19(n,γ)N20 and N20(n,γ)N21 excitation functions and thermonuclear reaction rates have been determined. The N19(n,γ)N20 rate is up to a factor of 5 higher at

On-line diagnostic tool for measurement of the time delay between two ultrashort light pulses

Ultrafast accelerator-based sources combined with synchronized femtosecond lasers are currently being developed. The method described here is intended as a jitter monitor at such facilities. We report on the possibility of extracting a time-offset signal between two different synchronized ultrashort light pulses. The method is based on sum-frequency generation in a nonlinear crystal. Aiming at extracting the time-difference from visible pulsed radiation from an x-ray undulator and femtosecond laser pulses we are investigating the possibility of obtaining timing information when one of the two pulses is very weak (10(6) photons/pulse). This will enable on-line monitoring of the relative timing of an accelerator-based free-electron laser and a synchronized visible laser. The spatial position of the sum-frequency mixed region is registered using a position sensitive detector (PSD). We show that for an 80 fs light source the described electronic equipment is capable of delivering a signal proportional to the temporal shift of different ultrashort light pulses with an accuracy of approximately 30 fs in a time interval of several ps

Systematics in the light response of BGO, CsI(T1) and GSO(Ce) scintillators to charged particles

The light response of a BGO crystal has been measured for particles Z = 1-8, A = 1-16 in the energy range similar to2-60 A MeV. The reaction products are identified by a DeltaE(Si) - E(Sci/PD) telescope, The position of the jump in the value of the signal from the PD at the punch-through points is used to calibrate both the DeltaE(Si) and E(Sci/PD) scales in MeV. The dependence of the light output on the energy E, ion atomic number Z and mass A is parameterized by the power law relation, L(Z, A, E) = a(1)((Z, A))E(a2(Z, A)). The parameters a(1) and a(2) have a smooth dependence on Z for all three crystals. The mass dependence of a(1), a(2) is deduced as a simple analytical expression, The systematics of these parameters is presented for BGO, CsI(Tl) and GSO(Ce) scintillators as a function of Z, A. Calculations of the response function, based on the Murray-Mayer model provide an excellent description of the shape of L(Z, A, E) versus E dependence, but show some deviations in the individual ion normalization constant for the BGO and GSO(Ce) scintillators. (C) 2002 Elsevier Science B.V. All rights reserved

Probing the liquid-gas coexistence in p+Xe reactions from 200 to 1400 MeV

The nuclear equation of state (EOS) is probed from statistical parameters, determined in an excitation function experiment on p + Xe-nat reactions at 200-1400 MeV. Total charge (Z) distributions follow a cascade-[multi]fragmentation-evaporation (CFEM) model well. The caloric curve in regions supposedly dominated by fast processes is compatible with a pure statistical multifragmentation (SMM) process, where the temperature (T)-excitation energy (epsilon*) relation starts in the Fermi liquid phase and progresses into a liquid/gas coexistence region, where it remains up to 1400 MeV. A local peak in T at epsilon* = 2.1 MeV agrees with the idea of sudden fragmentation. (c) 2006 Elsevier B.V. All rights reserved

CHICSi - a compact ultra-high vacuum compatible detector system for nuclear reaction experiments at storage rings. II. Detectors

We describe the detectors for identification of charged particles and fragments in CHICSi, a large solid angle multitelescope system mounted inside an ultra-high vacuum (UHV), cluster-jet target chamber. CHICSi performs nuclear reaction experiments at storage rings. The telescopes consist of a first very thin, 10-14 mum Si detector, a second 300 mum (or possibly 500 pm) ion implanted Si detector supplemented by a 6 mm GSO(Ce) scintillator read out by a photodiode (PD) or by a third 300 mum Si detector. The telescopes provide full charge separation up to Z = 17 and mass resolution up to A = 9 in the energy range 0.7-60A MeV. The thin p-i-n diode detector, etched out from a 280 mum Si wafer, and the GSO/PD detector, both exclusively developed for CHICSi, provide an energy resolution less than or equal to 8%, while the standard 300 mum detectors have less than or equal to 2% energy resolution. Radiation stability of the Si detectors is confirmed up to an integrated flux of 10(10) alpha particles. The GSO detector has 70% light collection efficiency with the optical coupling to the PD a simple open, 0.2 mm, gap. A new method, developed to perform absolute energy calibration for the GSO/PD detector is presented. (C) 2003 Elsevier Science B.V. All rights reserved