Lead-glass Counters Research Articles

Performance test of a lead-glass counter for the J-PARC E36 experiment

The J-PARC E36 experiment will search for a violation of lepton universality by a precise measurement of the ratio of the kaon decay widths RK=Γ(K+→e+ν)/Γ(K+→μ+ν). Charged particles will be identified by the combination of three independent systems: a lead-glass Cherenkov counter, an aerogel Cherenkov counter, and a time-of-flight measurement. The performance of the lead-glass Cherenkov counter was investigated with e+, μ+, and π+ beams in the relevant momentum region from the K+ decays. By using a polyethylene degrader to slow down the beam momentum in front of the lead-glass block, we succeeded in reducing the muon mis-identification probability down to 5% while maintaining a high e+ detection efficiency of 98%.

Performance of the electromagnetic calorimeter of the HERMES experiment

The performance of the electromagnetic calorimeter of the HERMES experiment is described. The calorimeter consists of 840 radiation resistant F101 lead-glass counters. The response to positrons up to 27.5 GeV, the comparison between the measured energy and the momentum reconstructed from tracking, long-term stability, hadron rejection and neutral meson invariant mass reconstruction are shown.

The electromagnetic calorimeter of the NOMAD experiment

Abstract A description is given of the NOMAD electromagnetic calorimeter, consisting of 875 lead-glass counters read out by two-stage photomultipliers and a low noise electronic chain. The detector operates in a 0.4 T magnetic field transverse to the counter axis. The paper discusses the design criteria, the lead-glass characteristics, the properties of the read out chain and provides a summary of the calorimeter performance.

Measurement of the left-right asymmetry in pi -p--> gamma n from 301 to 625 MeV/c at backward angles.

The left-right asymmetry of ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\gamma}n$ has been measured using a transversely polarized target at seven pion momenta from 301 to 625 MeV/c, mostly at photon angles of 90\ifmmode^\circ\else\textdegree\fi{} and 110\ifmmode^\circ\else\textdegree\fi{} c.m. The final-state $\ensuremath{\gamma}$ and neutron were detected in coincidence. Neutrons were recorded in two arrays of plastic scintillators and the $\ensuremath{\gamma}'\mathrm{s}$ in two matching sets of lead-glass counters. The results are compared with the predictions from the two most recent single-pion photoproduction partial-wave analyses. The agreement with the analysis of Arai and Fujii is poor, casting some doubt on the correctness of their values for the radiative decay amplitude of the neutral Roper resonance which are used widely. The agreement is much better with the results of the VPI analysis. Also, a comparison is made with the recoil-proton polarization data from the inverse reaction measured at 90\ifmmode^\circ\else\textdegree\fi{} with a deuterium target. It reveals substantial discrepancies, indicating the shortcomings of the deuterium experiments for neutron target experiments. Our data are also compared with several bag-model calculations.

Performance of the VENUS lead-glass calorimeter at TRISTAN

The initial performance of the VENUS barrel electromagnetic calorimeter at TRISTAN is described. The calorimeter is composed of 5160 lead-glass counters in a semi-tower arrangement. An energy resolution of 3.8% was obtained for 26 GeV Bhabha events. The neutral pions in the hadronic events were reconstructed with a mass resolution of σ = 16 MeV. The gain of the lead-glass counters was stable within 2% during a four months operation at TRISTAN.

Calibration and monitoring of the ARGUS shower counters

The 1760 shower counter modules of the detector ARGUS at DORIS II are monitored by a laser as the central light source. A lead glass counter, which also detects cosmic muons, and a photodiode serve as reference systems. The paper describes the technical layout, performance and stability of the monitoring system. Algorithms and corrections applied in the calibration procedure are discussed in detail. The monitoring system serves also to control the time-of-flight counter performance and to calibrate their TDCs.

Gamma Ray Source Using Internal Targets in the Tristan Accumulation Ring

As an alternative electron source TRISTAN AR is now operational, and is a$le to accelerate and store an electron beam of more than 5 GeV. We planned to extract high energy gamma rays by inserting a internal target into the AR, because a direct beam extraction is not easy. Two gamma ray lines are prepared by the two detector groups. Each detector group has its own target and gamma ray line. It is also required that the gamma rays should be simultaneously produced at the two targets with the least interference between them. The circulating electron beams gradually collide with the target and produce gamma rays, which are extracted from the AR through a Be-foil window. By a converter the gamma ray is changed into high energy electrons and positrons, which are finally used for the calibration of the lead glass counter. The momentum of the electron beam is defined by an analyzer magnet. At present two gamma ray lines, IT1 and IT4, are available as shown in Fig. 1, and are able to produce the electron beams for the two detector groups simultaneously. Target System Each internal target is located in the beam duct at a bending magnet gap and inserted horizontally from the outside of the beam orbit. The target is suffered from enormous synchrotron radiation and hence is made of molybdenum which is heat-resistive and easy to fabricate. The target head is 3 mm thick and 6 mm high, and is cooled by water flowing through a hole inside the target holder. The target position is monitored by a potentiometer and can be precisely adjusted within 0.05 mm by a remote control.

A test of dense lead glass counters

Energy resolution, position dependence of pulse height, and electron/pion separation for energies from 1 to 16 GeV were measured for lead glass arrays of newer, denser materials with radiation lengths of about 1.5 cm. The energy resolution typically was measured to be σ/ E = 1% + 4.5%/√ E.

Effects of light guides and optical filters for a high density lead glass counter

Effects of various light guides on energy resolution, position dependence of the output pulse and the hadron suppression factor were studied for a high density lead glass counter with particles of energies between 1 GeV and 16 GeV. The best hadron suppression factor was obtained for a configuration with a plastic light guide and a short wave cutoff filter at little expense to energy resolution. The energy resolution is worse at high energy and is dependent on the hit position of an incident particle for a BK7 light guide.

A measurement of the response of an SCG1-C scintillation glass shower detector to 2–17.5 GeV positrons

We have measured the response of an electromagnetic shower counter constructed from the new scintillation glass (SCG1-C, Ohara Optical Glass, Inc.) to positrons in the energy range 2 to 17.5 GeV. We have measured the energy resolution of this 18.4 radiation length detector plus its attendant SF5 lead glass shower counter array to be σ/ E = (1.64±0.14)%+(1.13±0.33)%/√ E with the constant term dominated by variations in the variations in the conversion point of the positron and shower leakage. We found this counter to be linear over the energy range examined. We have also measured the light output of the SCG1-C counter relative to light output of the SF5 lead glass guard blocks using 17.5 GeV positrons. We find that the SCG1-C counter produces 5.10±0.30 more light at the phototube than the SF5 lead glass counters.

Test results and practical evaluation of a magnetic field tolerant electromagnetic shower detector, based on a lead glass scintillator sandwich

We have made a transparent electromagnetic shower absorber, sandwiching together lead glass and scintillator sheets. The energy resolution we achieve is as good as expected for a sampling calorimeter with the passive layer thickness adopted, and the signal produced is about ten times larger than the signal from the Cherenkov radiation in the lead glass. We show that this makes possible the use of vacuum photodiodes with a noise level of the order of 40 MeV, and such a counter could therefore be operated in a magnetic field. Finally, we propose and discuss possible schemes for the production of large systems, arguing that the cost per counter would be significantly lower than an equivalent lead glass counter.

A Measurement of the Response of an SCG1-C Scintillation Glass Shower Detector to 2-17.5 GeV Positrons

We have measured the response of an electromagnetic shower counter constructed from the new scintillation glass (SCG1-C, Ohara Optical Glass, Inc.) to positrons in the energy range 2 to 17.5 GeV. We have measured the energy resolution of this 18.4 radiation length detector plus its attendant SF5 lead glass shower counter array to be σ/E = (1.64 ± 0.14)% + (1.13 ± 0.33)%/√E with the constant term dominated by variations in the conversion point of the positron and shower leakage. We found this counter to be linear over the energy range examined. We have also measured the light output of the SCG1-C counter relative to light output of the SF5 lead glass guard blocks using 17.5 GeV positrons. We find that the SCG1-C counter produces 5.10 ± 0.30 more light at the phototube than the SF5 lead glass counters.

Heavy liquid total absorption counter “helicon”

The results of a test using heavy liquid counters (HELICONs) as a total absorption counter (calorimeter) for electrons or photons are reported. The results indicate that some of them are already equivalent or even superior to an SF-5 lead glass counter with high resistivities against radiation damage. Discussions are given for using them as a practical calorimeter as well as for further development of HELICONs.

Computer controlled table positioner

With the purpose of constructing an automated calibration system for lead glass counters, simple auxiliary circuits have been constructed which bring an electric table positioner under the control of a computer. In this article, the circuits, their operations in positioning the table and the precision of positioning are reported, and how further to improve the precision is discussed.

Observation of the decay K L0→π ±π 0e ∓ν

The rare decay K L 0→π ±π 0e ∓ν has been observed in an experiment using a MWPC spectrometer and a lead glass counter hodoscope. The observed branching ratio Γ(K L 0→π ±π 0e ∓ν)Γ(K L 0→all)=(6.2±2.0) × 10 −5 agrees well with the theoretical prediction. The charged pion angular distribution was found to be consistent with l = 1 as expected from the |ΔI|=½ rule.

A measurement of the transverse momenta of partons, and of jet fragmentation as a function of √ s in p-p collisions

A large solid-angle apparatus consisting of a superconducting solenoid magnet, cylindrical drift chambers and two arrays of lead-glass counters was used to examine particles associated with a high transverse momentum trigger in p-p collisions with three √ s values at the CERN ISR. The trigger was given by energy deposition in lead-glass arrays centred at 90°. The trigger transverse momentum range covered was 3 < p T trig < 11 GeV c . Results are given for p out for both individual charged particles, and also for the sum of charged particle momenta in the hemisphere opposite to the trigger. Mean values are then deduced for the parton transverse momentum k T , and for the jet fragmentation momentum j T .

Automated Calibration System for Lead Glass Counters

An automated calibration system for lead glass counters has been developed. It has been used to calibrate about 2800 lead glass counters for the JADE experiment at DESY. In this article, we describe the configuration of the system, its control program and the calibration procedures.

A 207Bi light pulser for stabilization of scintillation and lead glass Cherenkov detectors

The design, fabrication techniques, and performance parameters are presented for a light pulser consisting of radioactive 207Bi embedded in capsulses of various types of plastic scintillator material. A typical resolution of 16% (fwhm) for the 0.974 MeV conversion electron line was obtained. A method whereby the contribution to the resolution due to photoelectron statistics can be separated from the total measured resolution is described. An application of these pulsers to the stabilization of an array of 60 lead glass counters is described.

On the choice of the photomultiplier size for total absorption counters at high energies

The resolution of the total absorption lead-glass counter was studied in a 25 GeV electron beam depending on the Cerenkov light collection conditions. It is shown that in the region of some tens of GeV and above small photomultipliers can be used in the counters covering only a small part of the radiator surface.

An LED monitoring system for a large lead-glass counter array

We have built and operated a system which monitors the gains of 318 lead-glass counters as a function of time with an accuracy of 1–2%. The light source is a single high-intensity yellow light-emitting diode (LED), and the light is transmitted to each of the counters by low-attenuation plastic optical fibers. The intensity of the LED light is measured by a reference scintillation counter whose gain is known from frequent 241AmNal light source and cosmic ray measurements. We present here details of the system and of its performance during a nine-month experiment at SPEAR.