Accurate spectra for high energy ions by advanced time-of-flight diamond-detector schemes in experiments with high energy and intensity lasers

Abstract

Time-Of-Flight (TOF) methods are very effective to detect particles accelerated in laser-plasma interactions, but they show significant limitations when used in experiments with high energy and intensity lasers, where both high-energy ions and remarkable levels of ElectroMagnetic Pulses (EMPs) in the radiofrequency-microwave range are generated. Here we describe a novel advanced diagnostic method for the characterization of protons accelerated by intense matter interactions with high-energy and high-intensity ultra-short laser pulses up to the femtosecond and even future attosecond range. The method employs a stacked diamond detector structure and the TOF technique, featuring high sensitivity, high resolution, high radiation hardness and high signal-to-noise ratio in environments heavily affected by remarkable EMP fields. A detailed study on the use, the optimization and the properties of a single module of the stack is here described for an experiment where a fast diamond detector is employed in an highly EMP-polluted environment. Accurate calibrated spectra of accelerated protons are presented from an experiment with the femtosecond Flame laser (beyond 100 TW power and ~ 1019 W/cm2 intensity) interacting with thin foil targets. The results can be readily applied to the case of complex stack configurations and to more general experimental conditions.

Transient electromagnetic fields generated in experiments at the PHELIX laser facility

“…A Time-Of-Flight (TOF) diamond detector [26] was installed at an angle of 90 ∘ degrees from laser axis, 𝑑 𝐷 = 152 𝑐𝑚 away from the target, behind the position of the D-dot and elevated above the Teflon wall, in order to obtain information about the ions accelerated in the direction of the field probe.…”

“…We obtained the reported measurement by acquiring the D-dot signal on two channels of the oscilloscope (using a calibrated signal splitter), set with different amplitude scales, in order to improve the signal-to-noise-ratio of the signal (using the same technique reported in Ref. [26]). The frequency-dependent signal attenuation, provided by the cable chain that connected the probe to the scope, was taken into account by performing a de-embedding procedure of the cables and adjusting the retrieved raw signal accordingly (see the last section, devoted to measurement techniques, for details).…”

“…Accepted manuscript where 𝑞 𝑒 is the electronic charge, and the radiation-ionization energy, 𝜖 𝑔 , is the average energy needed to create a free electron-hole pair inside the detector; in case of diamond detectors 𝜖 𝑔 = 13.1 𝑒𝑉 [42]. 𝐶𝐶𝐸 is the Charge Collection Efficiency of the detector and 𝑄 𝑐 is the amount of collected charge that can be estimated by performing a numerical integration of the detected signal 𝑉(𝑡) [26]:…”

Thomson parabola and time-of-flight detector cross-calibration methodology on the ALLS 100 TW laser-driven ion acceleration beamline

“…Since the TOF technique coupled with diamond detectors ensures an accurate measurement of the maximum proton energy, 42,46 this technique was used to validate the kinetic energy estimations obtained with the TP spectrometer using the aforementioned cross-calibration methodology of the field integrals (see Sec. III B).…”

“…These EMPs, which can reach orders of hundreds of kV/m, can affect all the electronic devices placed nearby the experimental chamber. The proton spectra recorded with the diamond detectors located at +6 ○ and −9 ○ were computed following the procedure described by Salvadori et al, 42 while the TP spectrometer allowed to simultaneously obtain the ion spectra at 0 ○ . The particle number estimation retrieved from the parabolic traces shown in Fig.…”