Fast x-ray detector system with simultaneous measurement of timing and energy for a single photon

Yoshimi

Fujieda

et al. 2019

Nature

Thorium-229 is a unique case in nuclear physics: it presents a metastable first excited state 229m Th, just a few electronvolts above the nuclear ground state. This so-called isomer is accessible by VUV lasers, which allows transferring the amazing precision of atomic laser spectroscopy to nuclear physics. Being able to manipulate the 229 Th nuclear states at will opens up a multitude of prospects, from studies of the fundamental interactions in physics to applications as a compact and robust nuclear clock. However, direct optical excitation of the isomer or its radiative decay back to the ground state has not yet been observed, and a series of key nuclear structure parameters such as the exact energies and half-lives of the low-lying nuclear levels of 229 Th are yet unknown. Here we present the first active optical pumping into 229m Th. Our scheme employs narrow-band 29 keV synchrotron radiation to resonantly excite the second excited state, which then predominantly decays into the isomer. We determine the resonance energy with 0.07 eV accuracy, measure a half-life of 82.2 ps, an excitation linewidth of 1.70 neV, and extract the branching ratio of the second excited state into the ground and isomeric state respectively. These measurements allow us to re-evaluate gamma spectroscopy data that have been collected over 40 years.

Section: Appendices a Detector System A1 Apd Detector And Readout Systemmentioning

confidence: 99%

X-ray pumping of the 229Th nuclear clock isomer

Yoshimi

Fujieda

et al. 2019

Nature

“…The energy spectra obtained in the actual NRS measurement at high count rate of more than 10 6 cps have been reported in our previous paper [15]. This is potentially useful for other types of measurements as well as the 229 Th NRS measurement, for example, depth selective Mössbauer spectroscopy by electron detection proposed in [24].…”

Section: Energy Measurement Methodsmentioning

confidence: 52%

“…We recently developed a fast single X-ray photon detection system by using thin Si-APDs [15]. It was developed for the synchrotron-radiation based nuclear resonant scattering (NRS) measurement of thorium-229 [16].…”

Section: Introductionmentioning

confidence: 99%

Energy response of X-rays under high flux conditions using a thin APD for the energy range of 6–33 keV

Nuclear Instruments and Methods in Physics Research Section A:

Hiraki

Kaino

et al. 2019

Self Cite

This paper reports on the demonstration of a high-rate energy measurement technique using a thin depletion layer silicon avalanche photodiode (Si-APD). A dedicated amplitude-to-time converter is developed to realize simultaneous energy and timing measurement in a high rate condition. The energy response of the system is systematically studied by using monochromatic X-ray beam with an incident energy ranging from 6 to 33 keV. The obtained energy spectra contain clear peaks and tail distributions. The peak fraction monotonously decreases as the incident photon energy increases. This phenomenon can be explained by considering the distribution of the energy deposit in silicon, which is investigated by using a Monte Carlo simulation.

“…The pellet was covered with two 20 Â 20 mm MgF 2 substrates, one on either side. The scattered X-ray photons were detected by a dedicated energy-sensitive X-ray detector (Masuda et al, 2017(Masuda et al, , 2019a.…”

Section: Nrs Measurementmentioning

confidence: 99%

Absolute X-ray energy measurement using a high-accuracy angle encoder

Watanabe

Beeks

et al. 2021

J Synchrotron Radiat

Self Cite

This paper presents an absolute X-ray photon energy measurement method that uses a Bond diffractometer. The proposed system enables the prompt and rapid in situ measurement of photon energies over a wide energy range. The diffractometer uses a reference silicon single-crystal plate and a highly accurate angle encoder called SelfA. The performance of the system is evaluated by repeatedly measuring the energy of the first excited state of the potassium-40 nuclide. The excitation energy is determined as 29829.39 (6) eV, and this is one order of magnitude more accurate than the previous measurement. The estimated uncertainty of the photon energy measurement was 0.7 p.p.m. as a standard deviation and the maximum observed deviation was 2 p.p.m.