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Precise knowledge of the energy and lifetime of 229mTh isomeric state has notable importance as a basis for a nuclear clock. Such a clock would be capable to extend precision on the oscillator frequency by up to four orders of magnitude compared to the presently best atomic clocks. However, the technique proposed for the clock requires that the isomeric state energy is accessible with existing laser systems. Previous measurement placed this state at ∼8 eV (150 nm), in the Vacuum Ultra Violet (VUV) range of the electromagnetic spectrum. A precise direct measurement of the energy of this state is necessary to determine whether the nuclear clock can be made using existing laser technology. We are developing a cryogenic microcalorimeter to measure the energy and lifetime of the 229mTh isomeric state directly. The experiment will use a 233U source whose alpha-decay will populate the 229mTh isomeric state with 2% probability. The subsequent decay of 229mTh will be measured by a Transition Edge Sensor (TES) with <1 eV resolution. Such a technique will allow to observe all possible types of decays of 229mTh in the range of energy from 3 to 50 eV and lifetimes >5 microseconds. The single-photon TES has sufficient resolving power combined with high efficiency in the whole energy band for this experiment. Here we present a prototype of TES based on a 200 nm thick iridium-gold (Ir/Au) film which was tested with a pulsed laser source and demonstrated ∼0.8 eV energy resolution and 5.8 ± 2.1 μs signal recovery time. [ABSTRACT FROM AUTHOR]

Diamonds are very promising candidates for the neutron diagnostics in harsh environments such as fusion reactors because of their proven radiation hardness. In comparison to the standard neutron diagnostics currently used (i.e., fission chambers, silicon based detectors, scintillators) CVD diamonds are less sensitive to $\gamma $ rays, which represents a huge background in fusion devices. Furthermore, their low leakage current provides a high energy resolution. A CVD diamond based detector has been proposed for the measurement of the 14 MeV neutrons from DT fusion reaction. The prototype was arranged in a proton recoil telescope configuration, featuring a plastic converter in front of the sensitive volume, in order to induce the (n, n) reactions which generate the recoil protons. The segmentation of the sensitive volume, achieved using two crystals with two dedicated electronic readouts, allowed to perform measurements in coincidence, which suppressed the neutron-carbon elastic scattering background. A preliminary prototype was assembled and tested at FNG (Frascati Neutron Generator), showing promising results regarding efficiency and energy resolution. [ABSTRACT FROM PUBLISHER]