Height analyzers

A typical procedure for Na assay is One gram proplnt samples sealed in polyethylene vials are irradiated for at least seven hrs in the thermal column. In order to minimize any thermal neutron flux gradient, the samples are rotated uniaxially at 60 rpm. Following irradiation, the samples are allowed to decay for approx 15 hrs to permit all short-lived radioisotopes to decay to insignificance. The 1.369 MeV 7-photopeak of each sample is then counted for 10 min with a 7.6cm x 7.6cm Na iodide scintillation detector coupled to a 400-channel pulse-height analyzer... 

The NAA measurements on the paper samples were made at the Breazeale Nuclear Reactor Facility at the Pennsylvania State University with a TRIGA Mark III reactor at a flux of about 1013 n/cm2-sec. Samples were irradiated from 2 to 20 min and counted for 2000 sec, after a 90 min decay time for Ba and a 60 hr decay for Sb, Analyses were performed instrumentally, without radiochemical separation, using a 35cm3 coaxial Ge-Li detector and a 4096-channel pulse height analyzer. With these procedures, detection limits for Ba and Sb were 0.02ug and 0.001 ug, respectively. These sensitivities are comparable to those obtained by GA s radiochemical separation procedure, and are made possible by the use of the higher neutron output from the more powerful reactor and in combination with the higher resolution solid state detector... 

The detector signal is conditioned through a single channel pulse height analyzer whose output pulses are fed to a scaler-timer in the single crystal controller. 

Data Analysis. All samples are analyzed for radioactive nuclides by a Ge(Li)-pulse height analyzer system calibrated for counting... 

Proportional Spectra of the Counter. The proportional pulses resulting from ionization of electrons and x-rays in the counter have been measured using a pulse height analyzer. Argon-37 and krypton-83m have been found to be excellent calibration gases. Argon-37, with a... 

Figure 11. Proportional spectra of (a) tritium and (b) argon-37 in 3 1 H2 CHh gas counting mixture at 400 cm. Hg pressure using R1DL-400 channel pulse height analyzer...

In the absence of a calibrated standard, the radioactivity in an argon-37 sample, supplied by Oak Ridge National Laboratory, has been approximated, using calibration data foar tritium and a pulse height analyzer to observe the peak. In the counter set up, a long line connects the counter to the fill system. The volume of the line is about 310 cm.3,... 

The electronic equipment used is now commercially available from three or four sources. Ours consisted of a Nuclear Science Instruments Mossbauer spectrometer and a Northern Scientific pulse height analyzer. The spectra we obtained were all fitted (by least squares) by an IBM 360 computer (7) used in a time-shared system. Plots were also computer-produced. All of our spectra, whether obtained by transmission or by scattering, are shown with the ordinate as fractional absorption relative to the off-peak background. 

Scattering intensity measured by the pulse height analyzer is related to particle size by calibration with monodisperse latex spheres or nearly mono-disperse NaCl particles. Calibration uncertainties have been studied and discussed (86-91). These studies show that the smallest particles that can be sensed by the ASASP probe are somewhat larger than the 0.12 xm stated by the manufacturer. Similarly, it is reported that detection of particles larger than about 2 xm is unreliable because of attenuation of the laser power. 

Figure 1. Block diagram of single-photon time-correlation apparatus from Barker and Weston 11 HV, high-voltage supplies L, lamp PI, photomultiplier M, monochromator FURN, furnace C, sample cell LP, light pipe F, interference filter P2, photomultiplier AMP, amplifier DISCI, discriminator D1SC2, discriminator T-S, timer scaler DL, delay line TAC, time-to-amplitude converter BA, biased amplifier MCPHA, multichannel pulse-height analyzer TTY, teletype printer and paper-tape punch REC, strip-chart recorder.

The cubic space group Pm3m (no systematic absences) was chosen for X-ray diffraction studies for reasons previously cited (9). Preliminary crystallographic experiments and subsequent data collection were performed at 2A°C with an automated, four-circle Syntex PI diffractometer, equipped with a graphite monochromator and a pulse-height analyzer. Molybdenum radiation was used for all experiments (Ka, X 0.70930 a K 2 ... 

Fig. 5. The schematic diagram of the pulsing system and the ion beam pulse radiolysis system with an optical emission spectroscopy. PMT denotes photomultiplier tube HV, high voltage supply CFD, constant fraction discriminator TAC, time to amplitude converter and PH A, pulse height analyzer. From Ref. 36...

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