L.M. Bollinger, et.al., Nucl. Instr. and Meth., A328, 221 (1993)  Home/Search   Document Not in Database   Summary   Related Articles   Check

....the 20 th subharmonic of the 2856 MHz frequency used for acceleration[4] The macropulse is 10 s long, and has a repetition rate of up to 10 Hz [5] The expected normalized rms emittance is 5 m with 1 nC per bunch. Electron beam diagnostics consist of current monitors and popup phosphor screens [6]. 4. Wiggler and Optical Cavity In the original CIRFEL configuration, the accelerator was connected to the wiggler through a 90 degree bend. The optical cavity mirrors were totally reflecting, and light was outcoupled through a hole in the downstream mirror. A smaller hole in the upstream mirror ....

J Krishnaswamy, et al. Nucl. Instr. and Meth. A 375 (!996) ABS22.

....13.16 6.73 Delta10 22 Gd 157.25 0.1 3. 28 Delta10 18 94 The thermal neutron capture cross section on natural gadolinium is dominated by the isotopes 155 Gd and 157 Gd which have capture cross sections of 61,400 and 255,000 barns and isotopic abundances of 14.8 and 15.7 , respectively [58]. This results in a natural gadolinium capture cross section of 49,100 barns, 82 of which is due to 157 Gd. The capture cross section on hydrogen is 0.328 barns [59] and on carbon, a negligible 3 Delta10 Gamma3 barns. Multiplying the cross section with the number density yields the ....

C.K. Hargrove, et al., Nucl. Instr. and Meth. A357 (1995) 157-169.

....enter the buffer or active cells, possibly to produce dangerous fast neutrons that could recoil in the target cells and subsequently capture on gadolinium, completing a fast slow neutrino like coincidence. The veto is constructed from 12 meter long opaque PVC cells left over from the MACRO [46] experiment. Six horizontal type cells, measuring 0:75 Theta 0:26 Theta 11:9 m, cover the top and bottom of the detector, and ten vertical type cells, measuring 0:23 Theta 0:49 Theta 11:7 m, cover each side. The cells are filled with a relatively low light yield liquid scintillator. ....

....side. The cells are filled with a relatively low light yield liquid scintillator. The ends of the detector will be covered by 10 cm thick liquid scintillator panels. The veto cells are read out by two 5 phototubes per end. From descriptions of the cell performance by the MACRO collaboration [46], it is calculated that muons going through the center of the MACRO cell will deposit at least 30 MeV, and will generate 300 photoelectrons at the phototubes. Accidental firing of the veto due to gammas from natural radioactivity would cause unnecessary dead time. Thus, the firing threshold should ....

S. Ahlen et al., Nucl. Instr. and Meth. A324 (1993) 337.

....Combining the measured values of n and Q #### , we can arrive at the initial charge from a 4.89 eV photon. We nd Q # 7000 1100. We can compare this to the theoretical value Q # n #### E ###### 1.7# ## 7200, where the factor of 1. 7 is the result of Monte Carlo calculations [8]. The number n #### 1.8 accounts for charge multiplication upon trapping and has been measured in our X ray detectors [9] The two values agree within error. 5. Conlusions We have begun the development and testing of imaging, single photon spectrometers. Our devices use superconducting tunnel ....

N. Rando et al., Nucl. Instr. and Meth. 313 (1992) 173.

....for critical density (# 2) An example of the dependence of # on v # is shown in Fig. 8, which shows a comparison of the # dependence of the average reduction in response computed for liquid krypton and liquid argon. The values of v # (E) and of the charge yield in argon are from Ref. [8]. The behaviour of the reduction of response is rather similar in the two liquids. Fig. 8. Average reduction of response vs. # in liquid krypton and liquid argon S. Palestini et al. Nucl. Instr. and Meth. in Phys. Res. A 421 (1999) 75 89 81 Fig. 9. Dependence of the response of the NA48 ....

V. Vuillemin et al., Nucl. Instr. and Meth. A 316 (1992) 71.

....stored on the electrodes. However, the presence of positive ions becomes relevant for detectors operated at large particle intensities, or when relatively low values of the bias voltage are desired. During the development of prototype liquid krypton calorimeters for the NA48 experiment at CERN [1], significant variations of response were observed when the intensity of an electron beam reached values corresponding to (1 2)# 10# GeV cm##s##, with the voltage bias set at 3 kV over a gap of 1 cm. The e#ect, which depended on the time within the beam burst, was due to space charge from ....

....cathodes. We see a modulation of the response with a peak to peak amplitude of 0.5 . The response is smaller when the shower core is closer to the electrodes, in particular the anode, where passive material and limited bandwidth in the read out electronics reduce the ability to extract the signal [1 3]. Since the energy weighted longitudinal (z) coordinate of the narrow shower core is di#erent from the weighted coordinate of the entire shower, the accordion geometry of the read out causes the position of minimum response to be shifted away from the center to the position xK 2mm. Fig. 16b ....

V. Fanti et al., Nucl. Instr. and Meth. A 344 (1994) 507.

....systems and we have identified a few bottlenecks that can be overcome. 9.1 LKr read out A description of the NA48 LKr read out has been published [11] The LKr calorimeter is read out by 40 MHz 10 bit FADC s. The dynamic range is further extended to 14 bits by means of a gain switching technique [12]. The detector is continuously digitised at 40 MHz and stored in a circular bu#er which over writes every 200 s. Upon receipt of a Level II trigger (time stamp command) the data are moved to another bu#er where they wait to be read out. One read out module (CPD) houses 64 channels. The read out ....

B. Hallgren et al, Nucl. Instr. and Meth, A, 419,680 (1998)

.... MARS [12] and MARS 2 [13] or the liquid krypton calorimeter KEDR [14] or they can have strong longitudinal zigzag structures like the accord ion shaped ATLAS liquid argon calorimeter [15] or longitudinal structures zigzagging slightly as in case of the NA48 liquid krypton calorimeter [16]. The first liquid argon sampling calorimeter was built by Willis and Radeka [17] in 1974. The calorimeter used 1.5 mm thick iron plates as absorber, spaced by 2 mm liquid argon as sensitive medium. Only 20 of the incident energy is seen by the liquid argon gap. The stochastic term of the energy ....

....electrode, the CuBe ribbons are guided by 5 spacer plates to Fig. 8. Read out cells with CuBe electrodes and spacer plate. perform a slight longitudinal zigzag. The impact point dependence is therefore reduced and can be represented by a unique correction function, which is the same for all cells [16]. Fig. 8 shows the details of the read out cell together with one spacer plate and the slight zigzag angle of 100 mrad. The active surface of the detector extends from a radius of 8 cm to an octagon shaped outer boundary. The circle, which can be drawn inside the octagon has a radius of 128 cm. ....

[Article contains additional citation context not shown here]

G.D. Barr et al., Nucl. Instr. and Meth. A 370 (1996) 413.

....plates with a thin read out electrode, to form a double gap chamber. The electrodes may be orientated at any angle with respect to the incident beam. They can be perpendicular to the incident beam, as in the liquid argon calorimeters MARS [12] and MARS 2 [13] or the liquid krypton calorimeter KEDR [14], or they can have strong longitudinal zigzag structures like the accord ion shaped ATLAS liquid argon calorimeter [15] or longitudinal structures zigzagging slightly as in case of the NA48 liquid krypton calorimeter [16] The first liquid argon sampling calorimeter was built by Willis and ....

....3.9 #E 4.04 #E Eq. 7) If ever built, the resolution of such a calorimeter would probably be better, due to natural clipping, i.e. short electron lifetime. The best resolution, so far published in noble liquid calorimetry, is the one obtained in the prototype of the quasi homogeneous KEDR [14] calorimeter. Their sampling fluctuation term is 1.6 #E. 4. Current sensitive calorimeters with longitudinal read out In all of the previously discussed electromagnetic calorimeters, the ionization chambers of the shower counters were orientated perpendicular to the incident particles. The ....

V.M. Aulchenko et al., Nucl. Instr. and Meth. A 379 (1996) 475.

....gap chamber or interleaving two absorber plates with a thin read out electrode, to form a double gap chamber. The electrodes may be orientated at any angle with respect to the incident beam. They can be perpendicular to the incident beam, as in the liquid argon calorimeters MARS [12] and MARS 2 [13] or the liquid krypton calorimeter KEDR [14] or they can have strong longitudinal zigzag structures like the accord ion shaped ATLAS liquid argon calorimeter [15] or longitudinal structures zigzagging slightly as in case of the NA48 liquid krypton calorimeter [16] The first liquid argon ....

....be the solution to the problem. This indeed reduces the sampling fluctuations, which are due to the energy sharing between active and passive layers of the calorimeter. However, it also increases (sampling) fluctuations, which are due to non uniform signal collection e#ciency in the active layer [13,17,18]. In an ionization chamber gap of an electromagnetic shower counter, secondary shower particles can either uniformly ionize the gap by traversing it fully or they can partially ionize the gap by being absorbed or created anywhere in the gap. The current due to the ion pairs produced by ionizing ....

[Article contains additional citation context not shown here]

C. Cerri et al., Nucl. Instr. and Meth. 227 (1984) 227.

....to form a single gap chamber or interleaving two absorber plates with a thin read out electrode, to form a double gap chamber. The electrodes may be orientated at any angle with respect to the incident beam. They can be perpendicular to the incident beam, as in the liquid argon calorimeters MARS [12] and MARS 2 [13] or the liquid krypton calorimeter KEDR [14] or they can have strong longitudinal zigzag structures like the accord ion shaped ATLAS liquid argon calorimeter [15] or longitudinal structures zigzagging slightly as in case of the NA48 liquid krypton calorimeter [16] The first ....

....a number n of fictitious electrodes is entered into to the wide gap of a shower counter. These fictitious electrodes are spaced by a distance, which is covered by a drifting electron in the time #, or they are spaced by a distance, corresponding to the shaping time t i . Two shower detectors [12,13], one sampling calorimeter with charge integrating read out consisting of many narrow active gaps and thin passive absorber plates and one quasi homogeneous calorimeter with initial current read out made of wide active gaps and few thin electrodes, were tested. Their results are compared with each ....

C. Cerri et al., Nucl. Instr. and Meth. 214 (1983) 217.

....power consumption. These results are also shown to be independent of temperature. 1 Introduction. The background current in the PAO FD PMTs will depend collectively on the sky brightness, and individually on the particular section of sky viewed by a single pixel. Data from dark nights in Utah [1] indicate that 40 photons m Gamma2 s Gamma1 deg Gamma2 will be arriving to the eye. Assuming an unobscured diaphragm area of 1:54 m 2 , a pixel field of view of 1:5 Theta 1:5 deg 2 , and a cathode efficiency of 20 , this value will translate into 2:7 phel (100 ns) Gamma1 or a DC ....

R. M. Baltrusaitas et al, Nucl. Instr. and Meth. A240 (1985) 410.

....are experimentally determined constants. In (A 1) it is assumed that the electron carrier emission probability (e N ) is larger than the hole carrier emission probability (e P ) The Boltzmann constant is denoted by k and E t is a constant with a value of 0.638 eV in Ref. 4] and 0.615 eV in Ref. [5]. We use the average of those two values (0.6265) in this paper, which means b = 7270 K. T is the absolute temperature (K) s P is the hole carrier trapping cross section, q is the electron charge, and P is the effective mass of the hole carrier, and N t is the density of defects. In the case ....

E. Barberis et al., Nucl. Inst. and Meth. A326 (1993) p 373-380.

....These curves (copied from main text Figure 3.2 4) represent worst case design charts even for ladders nested in concentric shells. k = 0.168, a = 1 9.532 and L = 250 mm. 5.0 APPENDICES 5. 1 APPENDIX I The leakage current density in a silicon detector has a complicated temperature dependence [4], which is given by: J leak = I leak Vol = qN t s P (3k P ) 1 2 3.87 x 10 16 T 2 exp( E t kT) NT 2 exp( b T) A 1) where b = E t k, and E t and N are experimentally determined constants. In (A 1) it is assumed that the electron carrier emission probability (e N ) is larger than ....

....E t k, and E t and N are experimentally determined constants. In (A 1) it is assumed that the electron carrier emission probability (e N ) is larger than the hole carrier emission probability (e P ) The Boltzmann constant is denoted by k and E t is a constant with a value of 0.638 eV in Ref. [4] and 0.615 eV in Ref. 5] We use the average of those two values (0.6265) in this paper, which means b = 7270 K. T is the absolute temperature (K) s P is the hole carrier trapping cross section, q is the electron charge, and P is the effective mass of the hole carrier, and N t is the density ....

M. Nakamura et al., Nucl. Inst. and Meth. A270 (1988) p 42-55.

.... uraniumliquid argon calorimeters with full coverage for a pseudorapidity 2 range up to (jjj 4:1) and hadronic coverage to (jjj 5:2) Jets are reconstructed using a cone algorithm with radius R = p Deltaj 2 DeltaOE 2 = 0:7 and are corrected with the standard D jet energy scale[15]. To measure the gap fraction 3 , the following event selection criteria were used: ffl Forward Jet Trigger: 2 jets with E T 12 GeV and (jjj 1:6) for both collider energies; we count the number of calorimeters towers which were above a given energy threshold (150 MeV for electromagnetic ....

B. Abbott et al. (D Collaboration), Nucl. Instrum. and Meth. in Phys. Res. A 424, 352 (1999).

....(p) typically leaving a rapidity gap in the direction of the parent proton. We thus examine the process p p jet jet X (for both forward and central jet production) and look for the presence of a forward rapidity gap along the 2 direction of one of the initial beam particles. The D detector [14] is used to measure jets and determine the fraction of forward and central jet events with forward rapidity gaps at p s = 630 and 1800GeV. These events are tagged at D by making use of their distinct event topology. Jets are measured in the uraniumliquid argon calorimeters with full ....

S. Abachi et al. (D Collaboration), Nucl. Instrum. and Meth. in Phys. Res. A 338, 185 (1994).

....DCA with a sign that is positive if the track intersects the direction of the associated jet in the direction of the jet s total momentum, negative if it intersects opposite to that direction. A jet is defined by grouping neighbouring calorimeter energy depositions, as described in Reference [14]. The angular resolution for the jet direction is 40 mrad. Tracks retained for the determination of D have to fulfil the following quality criteria: The angle, # j , between the track and its associated jet axis must satisfy cos # j 0.7. The track should have at least 30 hits spanning ....

O. Adriani et al., Nucl. Inst. and Meth. A 302 (1991) 53

....are: the long lifetime and hard fragmentation of b flavoured hadrons, the large lepton momentum in semileptonic decays and the broad event shape caused by the large b quark mass. The b tagging method using lifetime information relies on data taken with the L3 Silicon Microvertex Detector (SMD) [8] in 1994 1995. The method using the characteristic semileptonic decays of b hadrons relies on the good lepton identification and lepton energy resolution of the L3 detector. It requires lepton candidates with high momentum along and transverse to the direction of the associated jet, caused by the ....

M. Acciarri et al., Nucl. Inst. and Meth. A 351 (1994) 300

....high precision system of motors to insure correct alignment with the proton beam. 3. The 1 GHz Flash ADC An 8 bit 1 GHz Flash ADC module was developed for the tagging system to digitize photomultiplier pulses and to recognize superimposed double pulses of protons crossing the tagging detector [2]. The module contains two independent channels with up to 500 Megasamples per second implemented in commercial 8 bit 500 MHz hybrid FADC chips, each working with two internal 250 MHz data streams. They can be interleaved to obtain one channel with an e#ective sampling rate of up to 1 Gigasample ....

H. Bergauer et al., Nucl. Instr. and Meth. A 373 (1996) 213.

....seen in the tagger, the event is identified as a K # decay. To guarantee the correct identification of events in spite of the long flight path (216 m between tagger and hodoscope, corresponding to about 720 ns) all detectors of the experiment use one synchronized, highly stable global clock [1]. 2. The tagging detector To avoid pile up due to the high rate of over 10# protons s in the K # beam, an array of scintillation counters is used rather than a single scintillator. The tagging detector consists of a horizontal and a vertical ladder of thin scintillation counters, each of ....

....frequency for each 624 H. Bergauer et al. Nucl. Instr. and Meth. in Phys. Res. A 419 (1998) 623 631 Fig. 1. The tagging detector. channel. In NA48, the frequency actually delivered by the central clock is 960 MHz. For the sake of simplicity frequencies below are quoted for a 1 GHz clock input [1]. The external RESET signal is synchronised to the 1 GHz clock to give a precise starting point for the time information. During an external reset signal the synchronisation logic stops the 500 MHz clock. Then a few 250 MHz clock pulses are sent to the FADC chips to advance the internal states of ....

M. Jeitler et al., Nucl. Instr. and Meth. A 400 (1997) 101.

....to (1 2)# 10# GeV cm##s##, with the voltage bias set at 3 kV over a gap of 1 cm. The e#ect, which depended on the time within the beam burst, was due to space charge from positive ions. A confirmation was provided by data taken with a second prototype, which was tested at di#erent voltage values [2]. More recently, the NA48 calorimeter has been operated at reduced voltage in a kaon beam. E#ects of space charge have been observed in the central part of the detector [3] The purpose of this paper is to review the topic of space charge e#ects in parallel plate detectors, to describe less ....

....rate for liquid krypton, with X 1 cm and various voltage values. Fig. 5. Electron drift velocity vs. electric field, together with the e#ective value obtained by rescaling the free ion yield coe#cient (dashed line) Data on electron drift velocity in liquid krypton at 120 K are available [5,2]. Due to some inconsistencies we have chosen to use a parametrization based on a recent measurement made within the NA48 collaboration [6] The e#ects of recombination (free ion yield) and the behaviour for very low E values are included using the parametrization chosen for the NA48 simulation ....

[Article contains additional citation context not shown here]

G.D. Barr et al., Nucl. Instr. and Meth. A 370 (1996) 413.

....an Imaging Atmospheric Cherenkov Telescope (IACT) array observing very high energy (sub TeV) gamma rays from the universe. The four 10 m diameter telescopes can operate independently or as an array. The CANGAROO experiment is located in Woomera, South Australia. It started from a 3. 8 m telescope[1] (CANGAROO I) in 1992. The second stage, CANGAROOII, commenced in 1999 with the construction of a 10 m telescope mount with a mirror initially of 7 m diameter. The mirror was extended to 10 m in 2000 [2] CANGAROO III will be an array of four telescopes, with the existing CANGAROOII telescope ....

....the basic design parameters for the next three telescopes using the Monte Carlo technique. Similar studies have been carried out previously, for example by the VERITAS [3] and HESS [4] groups. We started from optimized parameters obtained by a previous study and our experience with CANGAROO I,[1] and verified those results. The pixel size and the telescope spacing were optimized. Also, some studies concerning the geomagnetic field effects and the possibility of large zenith angle observations were included. 2 Monte Carlo Electromagnetic and hadronic shower simulations in the air using a ....

Hara, T. et al, Nucl. Instr. and Meth., A332 (1993) 300.

....of the same data set used in the previous paper (Tanimori et al. 1998) in order to extract spectral information for the reasons mentioned above. 2 Analysis and Results Observations were done with the 3. 8m Cerenkov imaging telescope of the CANGAROO Collaboration (Patterson Kifune 1992; Hara et al. 1993) near Woomera, South Australia (136 # 47 E and 31 # 06 S) in 1996 and 1997. An imaging analysis using the conventional parameterization was applied for the data, where the parameter cuts were varied as a function of the energy of the shower. These variations of parameter cuts were estimated from ....

Hara, T., et al. Nucl. Instr. and Meth., A332, 300, 1993.

....which corresponds to a fairly substantial radiation dose, we have J leak (10 12 mm 2 , 0C) 5. 65 x 10 7 A mm 3 (A 9) The voltage required to fully deplete a detector that has received a fluence of 10 12 mm 2 over an extended period is a complicated function of its annealing history [7], but will be on the order of at least 150V. The required over biasing will raise the value of V b somewhat above that value. Putting all this together, we find that a typical value for the heat generation term late in the detector life is 18 m exp(aT) J leak V b = 5.65 x 10 7 A mm 3 x ....

H.J. Ziock et al., Nucl. Inst. and Meth. A342 (1994) p 96-104.

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L.M. Bollinger, et.al., Nucl. Instr. and Meth., A328, 221 (1993)

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