NeuLAND - FAIR

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Beamline Be exit window P 6 P 3 P 4 MRPC 124.5 28.5 10 Figure B.3.: Experimental setup at the ELBE facility, with approximate distances in cm. The MRPC unit is placed on a remote controlled moving table which allows 50 cm movement both in horizontal and vertical direction. The sizes of the plastic scintillators are (x/y/z) 20 mm × 20 mm × 5 mm (P3,4), 35 mm × 35 mm × 5 mm (P6). of operation of the ELBE accelerator was used, called one electron mode. In this mode, the gate voltage of the electron gun is reduced much below usual operating parameters. Then, most accelerated bunches are empty and the rest has only one electron per bunch [Nau-08]. Two scintillators were used as trigger in coincidence with the RF signal. The flux of single electrons was 5-20 Hz/cm 2 for the present measurements, much higher than can be obtained with cosmic rays. The electron beam first passes through 5 mm thick scintillator (P6) and then a thicker 20 mm scintillator (P3,4). The coincidence requirement defining an electron event is formed by P6 ∧ P3 ∧ P4 ∧ RF, meaning both photomultipliers of scintillator P3,4 and scintillator P6 detect a signal above threshold. In order to determine the time resolution, the time signal from the MRPC under study is compared with the reference time from the radio frequency signal (hereafter called RF signal) of the electron source. The high precision RF signal is supplied by the accelerator, with a jitter of less than 25 ps as measured with a digital oscilloscope. Therefore, no fast start detector is needed and the time resolution of the scintillators included in the setup is not critical. For the processing of the timing signal, two options are available: 1. FOPI FEE1-based readout: The RF signal is fed into a 25 ps per channel timeto-digital converter (TDC, CAEN V1290 2 ). The signals from the readout strips 2 CAEN S.p.A., internet address http://www.caen.it 102
Counts Counts 6000 5000 4000 3000 2000 1000 0 5000 4000 3000 2000 1000 0 0 10000 20000 30000 QDC scintillator P1,2 [25 fC] Figure B.4.: Scintillator charge spectra (units equivalent to P3,4 in figure B.3) for two different gate voltages of the electron gun: 9.5 V (top) and 6.5 V (bottom). In the top panel, the peaks due to 1, 2, 3, 4, 5, and 6 electrons per bunch are visible, as well as some low-charge background that is not correlated in time. In the bottom panel, just the peak due to one electron per bunch survives, due to the lower gate voltage and additional screens restricting the beam envelope. The mode of operation for the detector tests corresponds to the lower panel. of the MRPC under study are amplified by a FOPI FEE1 [Cio-07] frontend and fed into the subsequent TDC channels. The current signal is amplified by a factor of 30-70 in the front-end electronics and a further factor of 10 in the amplifier. The amplified charge signal is then fed into a 25 fC per channel charge-to-digital converter (QDC, CAEN V965). 2. TACQUILA-based readout: The TACQUILA-based readout [Koc-05] was used with the option for MRPC input. Since there was only one TACQUILA unit available at the time of the ELBE test shown here, the distance between readout ends was different, limiting the performance. The logic for the trigger and also various programmable scalers are implemented via software in a field programmable gate array (FPGA) unit that allows to change the trigger conditions on the fly for debugging the setup. The entire VME-bus data acquisition is controlled by a GSI multi-branch system (MBS) [Ess-00] unit. In order to reduce complexity and save cable length, all the electronics units are sited in the experimental cave, close to the setup. The experiment is then completely remote-controlled over the institute intranet. The beam quality is monitored during each experiment by checking the charge spectrum of the initial scintillator P1,2 (figureB.4). In this way it was assured that it still fulfills the single-electron per bunch mode. 103
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FAIR/NUSTAR/R 3 B/TDR NeuLAND Techn
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Germany EMMI and FIAS: Enrico Fiori
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INR Moscow: Alexander Botvina Russi
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Contents Executive Summary 11 1. In
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B.7. MRPC Solution using Glass as C
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Apart from the excellent energy res
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processes in the universe, such as
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decaying into 24 O plus 4 neutrons
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2. Physics Scenarios: Requirements
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e studied at R 3 B at FAIR include
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all theoretical calculations predic
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at the surface of the nucleus. The
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the evolution of fission channels (
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3. Summary of NeuLAND Prototype Res
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counts 70 60 50 40 30 20 10 0 15 15
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Figure 3.4.: Shown is the time reso
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4. Monte Carlo Simulations Within t
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normalized counts normalized counts
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GEANT3 interface. Here, we compare
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Counts 1000 900 800 700 600 500 400
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counts 5 10 4 10 3 10 2 10 10 LAND
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incident neutron fully active detec
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investigated. Three values for the
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spectrum, absorption length, refrac
Page 51 and 52: Counts 600 500 400 300 200 100 with
Page 53 and 54: Since, as discussed above, several
Page 55 and 56: events 800 600 400 200 0 0 200 400
Page 57 and 58: clusters N 100 50 0 0 500 1000 1500
Page 59 and 60: In the following section we discuss
Page 61 and 62: events 15000 10000 5000 input outpu
Page 63 and 64: events 2000 1500 1000 500 σ = 15 k
Page 65 and 66: 5. Technical Specifications and Des
Page 67 and 68: construction, or for subsequent rep
Page 69 and 70: positioning of 50 submodules mounti
Page 71 and 72: Figure 5.6.: Detector frame with fi
Page 73 and 74: 5.4. Peripheral Systems 5.4.1. Read
Page 75 and 76: Figure 5.12.: The photo shows the T
Page 77: 6. Radiation Environment and Safety
Page 81 and 82: 8. Calibration 8.1. Calibration wit
Page 83 and 84: Figure 8.3.: ToF distribution in 10
Page 85: Figure 8.4.: Event display for seve
Page 89 and 90: 10. Installation procedure, its Tim
Page 91: 11. Cost and Funding 11.1. Cost Est
Page 94 and 95: The timeline for milestone 1 includ
Page 96 and 97: 96 2. Sample Tests Random samples o
Page 98 and 99: PNPI St. Petersburg: G.D. Alkhazov,
Page 100 and 101: HV 1.$ mm 2$ mm 0+$1-2)-2'.%/ 5%4'.
Page 104 and 105: B.3. Design Issues Addressed with 4
Page 106 and 107: Time [ns] Counts 41 40 39 2200 2000
Page 108 and 109: Efficiency 100 80 60 40 20 0 7.5 8
Page 110 and 111: 200 AMeV, Erel = 100 keV emitted %
Page 112 and 113: B.7. MRPC Solution using Glass as C
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Page 116 and 117: [Bot-04] S. Botvina andI.N. Mishust
Page 118 and 119: [Lip-03] C. Lippmann, PhD Thesis, U
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NeuLAND - FAIR

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