Fission decay of N = Z nuclei at high angular momentum: 60^{60}Zn

Using a unique two-arm detector system for heavy ions (the BRS, binary reaction spectrometer) coincident fission events have been measured from the decay of $^{60}$Zn compound nuclei formed at 88MeV excitation energy in the reactions with $^{36}$Ar beams on a $^{24}$Mg target at $E_{lab}(^{36}$Ar) = 195 MeV. The detectors consisted of two large area position sensitive (x,y) gas telescopes with Bragg-ionization chambers. From the binary coincidences in the two detectors inclusive and exclusive cross sections for fission channels with differing losses of charge were obtained. Narrow out-of-plane correlations corresponding to coplanar decay are observed for two fragments emitted in binary events, and in the data for ternary decay with missing charges from 4 up to 8. After subtraction of broad components these narrow correlations are interpreted as a ternary fission process at high angular momentum through an elongated shape. The lighter mass in the neck region consists dominantly of two or three-particles. Differential cross sections for the different mass splits for binary and ternary fission are presented. The relative yields of the binary and ternary events are explained using the statistical model based on the extended Hauser-Feshbach formalism for compound nucleus decay. The ternary fission process can be described by the decay of hyper-deformed states with angular momentum around 45-52 $hbar$.Comment: 23 pages, 25 figure

Spectroscopy of 13B, 14B, 15B and 16B using multi nucleon transfer reactions

New information has been obtained on excited states of the neutron-rich boron isotopes $^{14}$B, $^{15}$B and $^{16}$B, using the reactions $^{12}$C($^{14}$C,$^{12}$N)$^{14}$B, $^{13}$C($^{14}$C,$^{12}$N)$^{15}$B and $^{14}$C($^{14}$C,$^{12}$N)$^{16}$B at about 24 MeV/A. The mass excess of $^{16}$B has been measured for the first time, it is 37.08(6) MeV. This means that $^{16}$B is unbound by only 0.04(6) MeV. Furthermore, the nucleus $^{13}$B has been investigated with the four reactions $^{16}$O($^{14}$C,$^{17}$F), $^{12}$C($^{14}$C,$^{13}$N), $^{12}$C($^{13}$C,$^{12}$N) and $^{12}$C($^{15}$N,$^{14}$O). Choosing different target-projectile combinations, it was possible to populate states with different selectivity. New states are observed in $^{13}$B at excitation energies above the threshold for two-neutron decay

Software modules of DAQ PCI board DeLiDAQ for positive sensitive MWPC detectors with delay line readout

The data acquisition system for the position sensitive delay line detectors on basis of the reprogrammable PCI DAQ board DeLiDAQ began to be used for scientific measurements with one and two dimensional position sensitive MWPC detectors on the neutron reactors IBR 2 JINR, Dubna and BERII HMI, Berlin . A stand alone version of the system with the graphical user interface on the basis of packet ROOT can be used on any PC with the operating system Windows 2000 or Windows XP. Architecture of the created software ensures several ways of interfacing to experiment control systems. In the paper we provide a description of the DeLiDAQ software modules, their features and results of some performance tests

Cross fertilization between spallation neutron source and third generation synchrotron radiation detectors

Suffering presently from relatively low source strengths compared to synchrotron radiation investigations, neutron scattering methods will greatly benefit from the increase of instantaneous flux attained at the next generation of pulsed spallation neutron sources. In particular at ESS, the strongest projected source, the counting rate load on the detectors will rise by factors of up to 50 150 in comparison with present generic instruments. For these sources the detector requirements overlap partly with those for modern synchrotron radiation detectors as far as counting rate capability and two dimensional position resolution are concerned. In this paper, examples of the current and forthcoming detector development, comprising e.g. novel solutions for low pressure micro strip gas chamber detectors, for silicon micro strip detectors and for the related front end ASICs and data acquisition DAQ systems, are summarized, which will be of interest for detection of synchrotron radiation as wel

A PCI DAQ board for MWPC detectors with high rate 2D delay line position readout

For high rate thermal neutron and e.g. also synchrotron radiation detection a PCI data acquisition DAQ board for readout of two dimensional position sensitive multi wire proportional chamber MWPC detectors with delay line position encoding was developed, and a first series of boards was produced and tested. The MWPC board comprises a deadtime less 8 channel multihit TDC chip of the F1 type with 120 ps LSB, a 40 MHz flash ADC, a FPGA, a FIFO, a 0.9 GFLOP DSP chip TMS320C6711 and a 256 MB histogram memory. For position encoding a position independent start and four position dependent stop signals are recorded from the MWPC anode and from either end of X and Y delay lines connected to the MWPC cathodes, respectively. Time of flight TOF can be measured with reference to a pulsed beam or chopper signal either with ge25 ns bin size for TOF ranges of up to 420 ms or alternatively with 120 ps LSB for ranges le16 ms. The pulse height of the MWPC anode signal is digitized in the flash ADC for neutron gamma and background discrimination. Hardware event filtering in the FPGA allows event rates up to 1 Mevents s by disentangling of two events occurring within the delay line time length of e.g. 250 ns. Whilst list mode data are recorded with full rate and full resolution on the host PC disk, 1D 3D histograms can be accumulated online in the on board HM for a fraction of the data and with reduced resolutio

Microstrip detectors with 157Gd converters

In the current 2004 2008 Joint Research Activity DETNI Detectors for Neutron Instrumentation in the EU Integrated Infrastructure Initiative for Neutron Scattering and Muon Spectroscopy NMI3 three detector types and a common ASIC and data acquisition board family are being developed. Two of these detector types, i.e. Silicon microstrip Si MSD and hybrid microstrip gas chamber MSGC detectors, are described in this article, both using thin 157Gd converters and aiming at two dimensional position resolutions of 50 100 m FWHM, pulse height readout for centre of gravity calculation and background suppression, time of flight TOF resolution lt; lt;1 s, and a counting rate capacity of 108 events s per detector module with single event counting. The third detector type is the CASCADE detector discussed in another articl