The first results of the observation of superradiance from a single, subnanosecond, high current, electron bunch passing through a wiggler immersed in a guide magnetic field are presented. The 300–500 ps microwave pulses were generated in the high gain regime for both the conventional and reverse directions of the guide magnetic field. The dependence of the radiation power on the interaction length as well as the absolute value of the power, 100–200 kW, were related with the development of self-bunching and consequently with coherent emission.

Experimental observation of wiggler superradiance under group synchronism condition

Total and partial charge-changing cross-sections of 600 A MeV Si14+ ions in a thick polyethylene target were measured by CR39 track etch detectors using an optical microscope DM 6000 M system installed with Leica QWin Plus software. The CR39 nuclear track detectors were used to identify the incident charged particles and their fragments using the cone-height distribution method. The charge resolution of CR39 detectors was achieved to be 0.17e in the present condition. The value of the total charge-changing cross-section was calculated to be σ
 tot
 = (766±17) mb. To calculate the partial charge-changing cross-sections for ΔZ = −11, −10, ..., −1, , number of events corresponding to each fragment were determined from multiple Gaussian fitting of cone-height distributions within 95.5% confidence level and the number of incident and survived beam ions were counted within 99.7% confidence level. Possible odd-even pattern in the values of the partial charge-changing cross-section is also presented. The measured charge pick-up cross-section for ΔZ = +1 is (7.2 ±1.7) mb.

Fragmentation cross-section of 600 A MeV Si14+ ions in thick polyethylene target

Calibration of CR39 detectors with new system for Fe26+ ion beam and measurement of total charge changing cross-section in Al target

Fragmentation cross sections of 788A MeV 28Si on carbon and polyethylene targets

Response of Cr39 detector to 5A GeV Si14+ ions and measurement of total charge changing cross-section

The production of fragmented nuclei from relativistic56Fe beam available from LBL Bevalac at 1.88A GeV has been studied using CR-39 (DOP) passive detector placed at an angle of 60° with respect to the beam. The histogram showing the experimental frequency distribution of minor axes of the elliptic etch pit shows the presence of the fragmented nuclei produced with charge numberZ from 25 up to 21. The histogram further reveals the presence of nuclei withZ=27 and 28. The production of nuclei heavier than56Fe is possibly due to the charge exchange or pick-up phenomena.

Fragmentation of56Fe in Al at 1.88A GeV

1.88A GeV56Fe beam of Lawrence Berkeley Laboratory BEVALAC irradiated at an angle 30° to the stack, composed of Al target and CR-39 (DOP) solid-state nuclear-track detector. These polymer sheets were etched in 6.25N NaOH solution at 70°C for 48 hours. The minor axes of the elliptic etch pits were measured by a Leitz Ortholux microscope. The measured projectile fragmentation cross-section for nuclei of chargeZ ranging from 21 to 25 is in approximate agreement with the calculated result from the semi-empirical nuclear fragmentation model after Wilson, Townsend and Badavi. The existence of trans Fe nuclei was noticed. The measured double-cone charge resolution was found to be 0.20e.

Study of fragmentation in56Fe+27Al interactions at 1.88A GeV using CR-39 (DOP) solid-state nuclear-track detector

Abstract Pershore made CR-39(DOP) solid state nuclear track detector was irradiated at a zenith angle of 30° by 238U-ions of energy 0.927 GeV/n using LBL BEVALAC beam. The exposed plate has been etched in 6.25N NaOH solution at 70°C for one hour. About 1094 cone lengths of the incident U-beam in CR-39(DOP) have been optically measured. The track registration sensitivity ( V T V G ) has been estimated and was found to be (127.7±10.5). The dependence of charge response of CR-39(DOP) detector on restricted energy loss of ultra heavy projectile ions has been studied, to explore the strong departure from Z2-dependence of the response function.

CR-39(DOP) as a Relativistic 238 U-Ion Detector

A search has been made on the charge-changing partial cross-sections by using 0.927 GeV/n238U ion from LBL BEVALAC projected at an angle 30° on27Al target and CR-39 (DOP) was used as analyser. The irradiated plastic sheets were duly etched for one hour in 6.25N NaOH solution and about 1680 cone lengths at both the surfaces of the CR-39 (DOP) sheets were optically measured. The cone length distribution exhibits the existence of U fragments in the charge range 84≤Z≤91 and the estimated partial cross-sections range from 60 to 400 mb. The present data are in accord with the fit to the extrapolated data of Binnset al.

Studies on elemental charge-changing cross-section for relativistic U+Al collisions using CR-39 (DOP) detector

Pershore made CR-39(DOP) solid state nuclear track detector was irradiated at a zenith angle of 30° by 238U-ions of energy 0.927 GeV/n using LBL BEVALAC beam. The exposed plate has been etched in 6.25N NaOH solution at 70°C for one hour. About 1094 cone lengths of the incident U-beam in CR-39(DOP) have been optically measured. The track registration sensitivity ( V T V G ) has been estimated and was found to be (127.7±10.5). The dependence of charge response of CR-39(DOP) detector on restricted energy loss of ultra heavy projectile ions has been studied, to explore the strong departure from Z2-dependence of the response function.

N. Durgaprasad

Papers

Fragmentation of56Fe in Al at 1.88A GeV

Study of fragmentation in56Fe+27Al interactions at 1.88A GeV using CR-39 (DOP) solid-state nuclear-track detector

CR-39(DOP) as a Relativistic 238 U-Ion Detector

Studies on elemental charge-changing cross-section for relativistic U+Al collisions using CR-39 (DOP) detector

Response of CR-39(DOP) as a relativistic 238U-ion detector