Multichannel analyzer calibration

Inductively Coupled Plasma. Analyses by ICP were performed on the same dissolutions used for the AA analyses for Cd and Pb. The solutions were diluted as necessary and were then nebulized and introduced into the plasma. Line spectra were collected with a multichannel analyzer and corrections were made for reagent blanks and background shifts. For all analyses, NBS Standard Reference Material 1632 was used for instrument calibration. 

Fig. 18. Schematic of apparatus used to measure fluorescence kinetics with a streak camera. The Nd glass laser emits a train of one hundred 1.06 pm pulses separated by 6 ns. A single pulse in the earlier portion of the train is selected by a Pockels cell and crossed polarizers (Pi and P2). The high voltage pulse ( 5 ns) at the Pockels cell is supplied by a laser triggered spark gap and a charged line. The single pulse ( 8 ps, 109 W) can be amplified. The second harmonic is generated from a phase matched KDP crystal. Beam splitters provide two side beams beam (1) triggers the streak camera beam (2) arriving at the streak camera at an earlier time acts as a calibrating pulse. The main 0.53 pm beam excites the sample for fluorescence measurement. The fluorescence collected with f/1.25 optics is focused into the 30 pm slit of the streak camera. The streak produced at the phosphorescent screen is recorded by an optical multichannel analyzer. (After ref. 67.)...

Spectrex ILI-1000 Particle Counter combines the Prototron with a Particle Profile Attachment (multichannel analyzer). The instrument has been used [118] for examining volcanic ash. AC Fine Dust was used for calibration in eight 5 pm steps, which indicated that accurate data was obtained for sizes above 2 pm. It has also been shown to correlate well with the more tedious filtration and counting method for large volume parenteral liquids [119]. Although semi-transparent containers or liquids reduce the amount of transmitted light flux, the instrument gives valid data for particulates in oil [120]. 

Most laboratories involved in radiation measurements now use personal computers and commercially available software for the analysis of y-ray spectra. Some of these programs allow the user to control the multichannel analyzer (MCA), calibrate the detector for various geometries, and provide analysis results. The programs are easy to use and do not require the user to be an expert in y-ray spectrometry. 

The decrease In americium concentration In the feed solution as a function of time was monitored with an on-line Nal(Tl) gamma detector and a Canberra Series 35 multichannel analyzer operating In the multlscalar mode. Most experiments were run with a dwell-tlme of 1 min., allowing >17 hours of continuous observation. The detector was calibrated by the use of solutions containing known amounts of americium. 

Fig.3. Different stages in processing of light intensity data. Plot A is the raw data (multichannel analyzer counts vs. time). Plot B is the calibration data. The stars show measured calibration points and the line shows the calibration equation obtained by fitting the starred data. Plot C is the current vs. time data after completing the calibration process. Plot D is the log of the absolute value of the current from plot C. The slopes correspond to a 2.7 /zs time constant for the forward step and a 3.0 /is time constant for the reverse step. The nominal RC time constant was 3.0 fis.

Figure 4.22 The analysis of the shaping amplifier output pulse heights into the x-ray energy spectrum, (a) A multiple-trace oscilloscope picture of the pulse-shaping amplifier output for a spectrum containing Mn and Ag K x-rays, (b) The analyzed pulse height spectrum as viewed on the multichannel analyzer display. Each dot represents one channel in the analyzer memory. The channel numbers have been calibrated in terms of x-ray photon energy. (Reprinted by courtesy of EG G ORTEC.)...

The Mossbauer measurement requires the generation of a precise, controllable relative motion between the source and the absorber. A large variety of drive systems has been developed. The majority of drives work on electromechanical, mechanical, hydrauHc, and piezoelectric principle. The spectrometers can be classified into constant-velodty spectrometers and velocity-sweep spectrometers. The mechanical drives, hke a lead screw or a cam, move with constant velocity. They have advantages for the thermal scan method and because their absolute velocity calibration is straightforward. The velocity-sweep spectrometers are usually of electromechanical nature (like loudspeaker-type transducers) and normally used in conjunction with a multichannel analyzer. The most commonly used M(t) functions are rectangular (constant velocity), triangular (constant acceleration), trapezoidal, and sinusoidal. A typical Mossbauer spectrometer is shown schematically in O Fig. 25.24. 

The block scheme of a Mossbauer spectrometer. A, absorber CR, cryostat with temperature controller TC (optional, for low-temperature measurements) S, source moved by velocity transducer VT of driving unit DR FG, function generator VC, velocity calibrator (optional) LI, laser interferometer (optional) DET, detector HV, high-voltage power supply PA, preamplifier AM, amplifier SCA, single channel analyzer MCA, multichannel analyzer and PC, computer, OP, output... 

The velocity calibration of the Mossbauer spectrometer is performed either by measuring the Mossbauer spectrum of standard materials or by a calibrator instrument measuring the absolute velocity of the source relative to the absorber. The latter can be achieved by counting the fringes from a Michelson interferometer with a laser source connected to the multichannel analyzer, and thus the velocity for each channel can be obtained. 

The essential components of a modem Mdss-bauer spectrometer as illustrated in the block-diagram of Figure 5 are the velocity transducer, the wave form generator and synchronizer, the multichannel analyzer, y-ray detection system, a cryostat or oven for low and temperature dependent measurements, a velocity calibration device, the source and the absorber, and a read-out unit. 

Besides the three major parts, modern Mossbauer spectrometers, to satisfy the requirement of high count rates, also utilize a fast pre-amplifier, a multichannel analyzer (which is now generally replaced by a computer or microprocessor), a calibration system (which is normally an interferometer) and a stable cryostat (such as simple He baths, He-flow cryostats, and He/" He refrigerators) during plotting of the Mossbauer spectrum. 

For the routine experiments of two TRIGA reactors and the commissioning experiments of the new 30 MW HANARO research reactor in the Republic of Korea, a stand alone system, with input signals independent from the reactor operation and safety chaimels, is configured. This system has been utilized for the criticality approach, real time reactivity measurement, noise analyses, control rod drop time measurement, and thermal power calibration in a natural convection cooled reactor. It replaces conventional counter modules for the criticality measurement, multichannel analyzer and... 

The MPC unit serves as the high-voltage source to the BF3 counter, and low-gain amplifier, and as a pulse inverter. The MPC switch is a convenient method of suddenly removing or restoring, the signal input to the multichannel analyzer for the time-versus-channel number calibration. 

Upon initial installation using the hardware approach of Fig. 44, the probe-head-injected intensity calibration path must be referenced against the ideal external calibration protocol to account for the probe optic s contribution to the measured spectrum. This is validated in all cases, as the probe optic is spectrally stable (unless fouled), and if this is anticipated, antifouling methods should be employed. The probe-head-injected neon wavelength calibration path is optically equivalent to the ideal external neon path for purposes of wavelength calibration being fed to the analyzer through the same optical fiber. Some industrial installations allocate one of the channels of a multichannel system, as shown in Fig. 45, to a sample compartment. This sample compartment can be used to either contain a permanent Raman standard, such as a sample of cyclohexane, or to run standard samples to improve or validate a calibration model. 

---