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An improved method for time-of-flight spectroscopy with an incompletely pulsed cyclotron beam
NUCLEAR
INSTRUMENTS
AND
METHODS
I3I
0975) 375;
© N O R T H - H O L L A N D P U B L I S H I N G CO.
AN I M P R O V E D M E T H O D FOR T I M E - O F - F L I G H T S P E C T R O S C O P Y W I T H AN I N C O M P L E T E L Y P U L S E D C Y C L O T R O N BEAM B. SIEBERT and R. J A H R
Physikalisch-Technische Bundesanstalt, D 33 Braunschweig, Bundesallee 100, Germany Received 17 October 1975 The method was irn proved by removing two restrictive assumptions on the number and energy of the satellite pulses.
When a cyclotron is used in neutron time-of-flight spectroscopy, an internal deflection system located near the ion source can be employed to pulse the internal cyclotron beam. However, because of multiturn extraction, one single accelerated pulse of ions may be split into one or more advanced and retarded satellite pulses in the extracted beam which then accompany the main pulse. This effect reflects itself in the pulsing properties of the neutron source and disturbs the time-of-flight spectra. In a previous paper 1) it was shown that a beam of this kind is still suitable for neutron time-of-flight spectroscopy, since the " t r u e " spectrum can be inferred by mathematical deconvolution of the measured spectrum. At the time of publishing, however, we had to make two restrictive assumptions: 1) One single retarded and one single advanced satellite pulse only are encountered. 2) The energy difference between the particles of the main pulse and the particles of the satellite pulses is negligible compared with the overall energy resolution of the experiment under study. Both assumptions do not generally hold in practical
375
cases. Regarding the second assumption, an energy difference between the particles of the main pulse and the particles of the satellite pulses should arise from the fact that, for instance, the particles of the first advanced satellite pulse experience one turn less inside the cyclotron compared with the particles of the main pulse. Consequently, the particles of the first retarded satellite pulse experience one additional turn inside the cyclotron, etc. Meanwhile we have developed a new unfolding technique, which allows for an arbitrary number of satellite pulses under the condition that the sum of the intensities of the satellite pulses is lower than the intensity of the main pulse. Moreover, small, but not negligible energy differences between successive pulses are taken into account. A comprehensive report 2) in German is available on request.
References 1) B. Siebert and R. Jahr, Nucl. Instr. and Meth. 119 (1974) 445. 4) B. Siebert and R. Jahr, PTB-Bericht ND-9 (1975).
INSTRUMENTS
AND
METHODS
I3I
0975) 375;
© N O R T H - H O L L A N D P U B L I S H I N G CO.
AN I M P R O V E D M E T H O D FOR T I M E - O F - F L I G H T S P E C T R O S C O P Y W I T H AN I N C O M P L E T E L Y P U L S E D C Y C L O T R O N BEAM B. SIEBERT and R. J A H R
Physikalisch-Technische Bundesanstalt, D 33 Braunschweig, Bundesallee 100, Germany Received 17 October 1975 The method was irn proved by removing two restrictive assumptions on the number and energy of the satellite pulses.
When a cyclotron is used in neutron time-of-flight spectroscopy, an internal deflection system located near the ion source can be employed to pulse the internal cyclotron beam. However, because of multiturn extraction, one single accelerated pulse of ions may be split into one or more advanced and retarded satellite pulses in the extracted beam which then accompany the main pulse. This effect reflects itself in the pulsing properties of the neutron source and disturbs the time-of-flight spectra. In a previous paper 1) it was shown that a beam of this kind is still suitable for neutron time-of-flight spectroscopy, since the " t r u e " spectrum can be inferred by mathematical deconvolution of the measured spectrum. At the time of publishing, however, we had to make two restrictive assumptions: 1) One single retarded and one single advanced satellite pulse only are encountered. 2) The energy difference between the particles of the main pulse and the particles of the satellite pulses is negligible compared with the overall energy resolution of the experiment under study. Both assumptions do not generally hold in practical
375
cases. Regarding the second assumption, an energy difference between the particles of the main pulse and the particles of the satellite pulses should arise from the fact that, for instance, the particles of the first advanced satellite pulse experience one turn less inside the cyclotron compared with the particles of the main pulse. Consequently, the particles of the first retarded satellite pulse experience one additional turn inside the cyclotron, etc. Meanwhile we have developed a new unfolding technique, which allows for an arbitrary number of satellite pulses under the condition that the sum of the intensities of the satellite pulses is lower than the intensity of the main pulse. Moreover, small, but not negligible energy differences between successive pulses are taken into account. A comprehensive report 2) in German is available on request.
References 1) B. Siebert and R. Jahr, Nucl. Instr. and Meth. 119 (1974) 445. 4) B. Siebert and R. Jahr, PTB-Bericht ND-9 (1975).