1,721,442 research outputs found
MEASURED RESPONSE OF AGED AND LARGE VOLUME NE104 AND NE110 SCINTILLATORS TO FAST PROTONS, NEUTRONS AND ELECTRONS
No full textThe pulse-height response of aged and large volume NE104 and NE110 organic scintillators was probed and neutrons in the energy range 10-60 MeV and with electrons of 113 MeV. For both counters the timing performance was tested with electrons. The effects of time on pulse-height response and timing performance are presented
A TOTAL ABSORPTION RANGE TELESCOPE - THE CARUZ
No full textA total absorption range telescope, the CARUZ, has been constructed, calibrated and employed in a coincidence experiment at TRIUMF. The CARUZ measures time-of-flight (TOF), energy (E), differential energy (ΔE) and range quantities. The energy resolution of the CARUZ for 50 MeV pions is measured to be 2 MeV and is 2 MeV for 70 MeV protons. The measured quantities enable the CARUZ to easily discriminate π+ of energy 8–60 MeV from electrons or positrons, and from protons of energy up to 140 MeV. The response of the scintillators to the stopping pions was measured. With the inclusion of the energy from the decay muon, the response of the scintillators is almost linear in incident π+ energy. The response of the stopping π+ alone is fitted to Birk's formula with a result for the product kB = 0.0114 ± 0.0017 (cm/MeV)
INCLUSIVE NEUTRON, PROTON AND DEUTERON ENERGY SPECTRA FROM STOPPED PI- ABSORPTION IN LI-6, BE-9, O-16 AND AL-27
No full textInclusive energy spectra (E ⩾ 20MeV) of neutrons, protons, and deuterons emitted after stopped π− absorption in 6Li, 9Be, 16O and 27Al (neutrons only) were measured. Single-neutron emission rates of the order of 10−2 and 10−3 per stopped pion were obtained for 6Li, 9Be, 16O and for 27Al respectively. The experimental data indicate a predominant contribution of two-nucleon absorption mechanism to the neutron and proton spectra for all the studied nuclei, and presence of direct deuterons from cluster-absorption for 6Li. Values of Rnp are deduced, which are consistent with predictions based on the absorption mechanism by a correlated pair of nucleons with pion rescattering
A Method for monitoring the stability of photomultipliers
No full textA method for monitoring hundreds of photomultipliers has been developed in conjunction with the first level trigger of the pion spectrometer CHAOS being constructed at TRIUMF. The system for monitoring the photomultiplier gain stability simply consists of a xenon lamp which operates in the nanosecond time region, a light guide which diffuses the light, and bundles of optical fibers which transport the light to photocathodes. The photomultiplier gain stability can be probed up to few percent (FWHM)
A counter for the identification and the energy determination of light charged particles and neutrons of energies in the range 20-100 MeV
No full textA large area plastic scintillator counter is described which is used for identifying the mass of light charged particles (p, d, t) of 20–100 MeV with a β-range-energy method, and for measuring their energies as well as that of neutrons of about the same energy by means of the time-of-flight method with a time resolution of 380 ps. The counter is used in an experiment concerning the stopped negative pion absorption in light nuclei. It could be used, however, in other experiments where the identification and the energy measurement of p, d, t, and n in the aforesaid energy range are required
The CHAOS Fast Trigger: An Array of telescopes for e, pi and p mass identification in the intermediate-energy region
No full textThe CHAOS Fast Trigger (CFT) is a system of 20 telescopes of plastic scintillator and lead-glass detectors, designed for the discrimination of charged e, π, p (and d) particles in the momentum range 40 to 400 MeV/c for e and π, and from 200 to 800 MeV/c for p. The results from a test measurement performed at TRIUMF show that the π-p and the π-e discrimination efficiency (i.e. the percentage of particles identified) is > 99% and > 90% in the whole momentum range, respectively. The π-e discrimination efficiency has been improved to > 93% through the application of neural networks
Analysis of the readout of a high rate MWPC
No full textAn analytical method to reduce the raw data supplied by a high-speed multiwire proportional chamber (MWPC) is presented. The results obtained with the MWPC and the associated readout system, LeCroy PCOS III, when monitoring a high-intensity flux of positive pions delivered by the M11 channel at TRIUMF are discussed. The method allows the flux intensity, the beam envelope and the detector efficiency to be determined with little uncertainty (few %) at intense particle beams ( > 107 particles/s)
Threshold behavior of the pi+ pi- invariant mass in nuclei
No full textWe present π+π− invariant-mass distributions between 300 and 380 MeV for the 2H, 4He, 16O, View the MathML source reaction at an incident π+ energy of 280 MeV. A prominent feature is the shift of their maximum downward to the 2mπ threshold as A increases. This behaviour finds a qualitative explanation in the framework of a model that investigates the modification of the strength function for an interacting (ππ)I = L = 0 system embedded in the nuclear medium. Also, the π+π− invariant-mass cross sections are compared with the predictions of an A(π+, π+π−) model that uses a microscopical approach for the elementary process of pion production, πN → ππ N. Four-fold differential cross sections as a function of the energy of outgoing π+ and p, and missing-mass distributions for the A(π+, pπ−) reaction are also presented for some of the examined nuclei. The experimental results are discussed within the framework of the two available models
(p, alpha) reactions on 1p, 2s-1d shell nuclei
No full textThe 12C(p, α)9B and 32S(p, α)29P reactions have been studied at incident energies of 42.77 and 41.9 MeV, respectively. The experimental (p, α) relative cross sections are well reproduced by distorted wave direct pickup calculations with a semimicroscopic form factor and current shell model wave functions. A comparison between (p, α) and (3He,d) spectra on 1p and 2s-1d shell nuclei, leading to the same final nucleus, shows a clear evidence of a dominant pickup process over the knockout mechanism in the dynamics of the (p, α) reaction
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