R. G. Pillay

Highly efficient and electrically robust carbon irradiated semi-insulating GaAs based photoconductive terahertz emitters

We demonstrate here an efficient photoconductive THz source with low electrical power consumption. We have increased the maximum THz radiation power emitted from SI-GaAs based photoconductive emitters (PCEs) by two orders of magnitude. By irradiating the SI-GaAs substrate with Carbon-ions up to 2 μm deep, we have created lot of defects and decreased the lifetime of photo-excited carriers inside the substrate. Depending on the irradiation dose, we find 1 to 2 orders of magnitude decrease in total current flowing in the substrate, resulting in subsequent decrease of heat dissipation in the device. This has resulted in increasing maximum cut-off of the applied voltage across PCE electrodes to operate the device without thermal breakdown from ∼35 V to >150 V for the 25 μm electrode gaps. At optimum operating conditions, carbon irradiated (1014 ions/cm2) PCEs give THz pulses with power about 100 times higher in comparison to the usual PCEs on SI-GaAs and electrical to THz power conversion efficiency has improv...

Electromagnetic transition from the 4+ to 2+ resonance in 8Be measured via the radiative capture in 4He + 4He.

An earlier measurement on the 4+ to 2+ radiative transition in 8Be provided the first electromagnetic signature of its dumbbell-like shape. However, the large uncertainty in the measured cross section does not allow a stringent test of nuclear structure models. This Letter reports a more elaborate and precise measurement for this transition, via the radiative capture in the 4He + 4He reaction, improving the accuracy by about a factor of 3. Ab initio calculations of the radiative transition strength with improved three-nucleon forces are also presented. The experimental results are compared with the predictions of the alpha cluster model and ab initio calculations.

Theg-factor of the 659 keV level in117In

We have measured theg-factor of the 659 keV, 3/2+, state in117In, using time differential perturbed angular correlation technique. The spin precession of this state was measured in an external field of 20·2 kG. The values of the Larmor precession frequencyω and theg-factor are obtained to be (60·1±0·3)106 rads/sec and 0·625±0·007 respectively.

A triple axes multiple target holder assembly

A triple axes multiple target holder assembly has been designed and fabricated to accommodate 27 targets to be used inside a high vacuum scattering chamber. This target holder assembly has been used satisfactorily in ion solid collision experiments using heavy ion beams from an accelerator.

Hexadecapole deformation studies in148,150Nd

Theγ-ray yields from inelastically excited 2+ and 4+ levels of144,146,148,150Nd nuclei using16O beam at near barrier energies in coincidence with the back-scattered projectiles were measured. The 2+ and 4+ level cross-sections were deduced from the measuredγ-ray yields and fitted to the DWBA calculations to obtain the reduced transition matrix elementsM(E4: 0+ → 4+). The deducedM(E4) values for148Nd and150Nd nuclei, 0.16(0.05) and 0.22(0.12) eb2, respectively are consistent with theoretical predictions.

A simple post-accelerator foil stripper assembly for atomic collision experiments

A multiple foil holder for use in ultra high vacuum (UHV) environment as a post accelerator ion stripper has been designed and fabricated. It is used to produce beams of an ion in different charge states at a given energy from a 14 MV pelletron accelerator. These ions are required in several types of atomic collision experiments. The assembly is tested with32S ions at various energies.

Giant dipole resonance studies in Ba isotopes at E/A≈5 MeV

Exclusive measurements of high energy

New limit for the half-life of double beta decay of 94Zr to the first excited state of 94Mo

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Characterization of PARIS LaBr3(Ce)-NaI(Tl) phoswich detectors up to Eγ ∼ 22 MeV

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Estimation of low energy neutron flux (En ⩽ 15 MeV) in India-based Neutrino Observatory cavern using Monte Carlo techniques

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