M. "Osakabe

M. Isobe

M. Sasao

T." Iida

National Institute for Fusion Science (NIFS-Repository)

§3. Development of Active Divider for Magnetic-Field Resistive Photo-Multiplier Osakabe, M., Isobe, M., Sasao, M., !ida, T. (Osaka Univ.) In D-T and D-D fusion experiment, the measurement of neutron detection is very important to obtain the information of fusion reactivity and fast ions. In such experiments on magnetically confined plasma devices, the effect of magnetic field on neutron detector and the saturation of the detector must be avoided. During TFrR discharges, the degradation of PMf gain of a COTETRA neutron spectrometer was observed due to the effect of magnetic field and the saturation of PMT. To overcome this defect, a HAMAMATSU R2490-07 was applied to reduce the effect of magnetic field. An active divider[ 1 ,2] was developed for this PMT to avoid the saturation. Figure 1 shows the electronic circuit. The divider current was driven by seven pairs of inverted darlington transistors at the last seven stage, and each dynode voltage was kept by reference resistors (R3). When -2k V of high voltage was applied to the divider without any light source, the current of 3.63mA was supp~ied. Using OKTA VIAN D-T neutron generator at Osaka University, the petformance of this _active divider was tested and compared with the normal (passive) resistive chain divider, which is available from HAMAMATSU Photonics. Fig. 2(a) shows the pulse height spectrum (PHS) of NE1 02A plastic scintillator for D-T neutrons obtained by a passive divider, and Fig.2(b) shows that obtained by an active divider. The counting rate of the detector was measured for the case of passive divider at 1.5x10S cps, and those for other cases were obtained by comparing the D-beam current at T-target of OKTA VIAN. As shown on Fig.2(a), the edge position of the PHS is decreasing from -1500 channel to ~00 channel as the counting rate of the detector is increasing for the passive divider. On the other hand, those of the active divider stay at -1000 channel up to 6x10S cps and the deterioration of edge position is small even for the case of 2.4x105 cps. This shows the effectiveness of the active divider for the use of high counting rate environment. 118 Authors wish to thank Dr. N.Sasao at Kyoto Univ. and Dr. G.A.Wurden at LANL for their useful suggestions on the active divider. We also wish to thank the stuff of the OKT AVIAN for their help at the test of the dividers. Fig.l Schematic drawing of the electronic circuit for the active divider. The character R and C express resistors arx:i capacitors, respectively. The value of each resistors ao:i capacitors are; Rl (33kW), R2 (34kW), R3 (lMW), R4 (84kW), R5 (50W), R6 (3.9kW), R7 (lOkW), Cl (O.OlmF), C2 (0.022mF), C3 (0.047mF), C4 (O.lmF), C5 (0 .. 22mF), and C6 (0.47mF). a) Passive Divider [channd] b) Active Divider -0-t.sxto• cp _._3.0r.!Os cp -Q-6.oxto• cp -l.4xl06 cp -0-t.sxto• cp ..... _ 3.0Xl0 1 cp -D--6.0x 10 J cp -1.2xl0 6 cp --6-l..4xl0 6 cp 10 I a............-.........I.~........._ ........................ ,.I.IJ..Io.L..u..KI..ooiLZAI-....a... ........... ..L...o....o. ................................. 0 500 1000 1500 lOOO 1500 3000 3500 4000 [channd] Fig.2 Pulse height spectra of NE102A for D-T neutrons. (a)Spectra obtained by passive divider. (b) Spectra obtained by active divider. References [1] G.A. Wurden et al., Rev. Sci. Instrum. 66 (1995), 901 [2] Y.Takeuchi, Mas. Thesis, Kyoto Univ. (1996) 

Development of Active Divider for Magnetic-Field Resistive Photo-Multiplier

Abstract

Similar works

Full text

Available Versions

National Institute for Fusion Science (NIFS-Repository)