Characterization of Diamond and Silicon Carbide Detectors With Fission Fragments

At a Glance

Metadata	Details
Publication Date	2021-09-20
Journal	Frontiers in Physics
Authors	M.-L. Gallin-Martel, Yeul Hong Kim, L. Abbassi, A. Bès, C. Boiano
Institutions	Institut des Matériaux, de Microélectronique et des Nanosciences de Provence, Centre National de la Recherche Scientifique
Citations	5
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Fission Fragment Detection

Reference: Gallin-Martel et al. (2021). Characterization of Diamond and Silicon Carbide Detectors With Fission Fragments. Frontiers in Physics, 9:732730.

Executive Summary

This research validates high-purity Single Crystal Diamond (SCD) detectors as the superior solid-state solution for high-rate, radiation-hard Fission Fragment (FF) detection, crucial for applications like the FIPPS spectrometer.

World-Class Timing: A 50 µm thick SCD detector achieved an exceptional time resolution of 10.2 ps RMS for 90 MeV FF98, the best value reported for diamond to date.
High Energy Resolution: SCD demonstrated superior energy resolution (~1.4% RMS) compared to Polycrystalline Diamond (pCVD) and Silicon Carbide (SiC) detectors (~3.4% RMS).
Material Differentiation: High-quality SCD significantly outperformed pCVD, which suffered from poor charge collection efficiency (CCE) and surface inhomogeneity due to grain boundaries.
Critical Application Validation: The results confirm the viability of SCD detectors for in-beam FF detection in intense thermal neutron environments, offering high speed and radiation hardness.
Pulse Height Defect (PHD) Identified: A significant PHD was observed in SCD (~50% charge loss), suggesting the need for optimization in detector geometry (e.g., thinner detectors) and higher electric fields to mitigate charge recombination in the Bragg peak region.
6CCVD Value Proposition: 6CCVD specializes in the thin, high-purity SCD materials (down to 0.1 µm) and custom metalization required to replicate and advance this high-performance instrumentation.

Technical Specifications

The following hard data points were extracted from the characterization of the SCD and SiC detectors using Fission Fragments (FF98, FF144) and alpha particles.

Parameter	Value	Unit	Context
Best Timing Resolution	10.2 ± 0.2	ps RMS	SCD (500 µm thick), FF98 @ 90 MeV
Best Energy Resolution	1.4	% RMS	SCD (50 µm thick), FF98 @ 70-100 MeV
SiC Energy Resolution	3.4	% RMS	SiC (400 µm thick), FF98 @ 70-100 MeV
SCD Thickness Tested (Thin)	50	µm	Detector B (Achieved best resolution)
SCD Thickness Tested (Thick)	517	µm	Detector A
pCVD Thickness Tested	300	µm	Detectors C, D, E, F
SCD Bias Voltage (Detector B)	-200	V	Corresponds to 4 V µm^-1 electric field
SCD Bias Voltage (Detector A)	-450	V	Corresponds to 0.9 V µm^-1 electric field
Pulse Height Defect (PHD)	~50	%	Loss of initial generated charge carriers in SCD for FF
Charge Collection Efficiency (SCD A)	100	%	Measured using 5.5 MeV alpha source
Charge Collection Efficiency (pCVD C)	30	%	Measured using 5.5 MeV alpha source (due to inhomogeneity)

Key Methodologies

The experimental characterization relied on precise material selection, specialized detector housing, and advanced signal processing techniques at the LOHENGRIN spectrometer.

Detector Types: Characterization utilized high-purity Single Crystal CVD (sCVD), Polycrystalline CVD (pCVD), and Diamond-on-Iridium (DOI) detectors, alongside a 4H-SiC p⁺n diode.
Detector Configuration: Diamond detectors were mounted in a “sandwich” configuration with 50 Ω adapted impedance holders, allowing reversible bias and signal readout from both sides (0° and 180°).
Metalization Schemes: Various metal contacts were employed:
- LPSC detectors (A, C, F): Aluminum (Al) disk-shaped metallization (50 nm or 100 nm thick).
- IFJ-PAN detector (B): Diamond-like-carbon (DLC), Platinum (Pt), and Gold (Au) layers (3 nm, 16 nm, 20 nm thickness, respectively).
- SiC detector: Nickel/Titanium (Ni/Ti) and Aluminum (Al) ohmic contacts.
FF Beam Source: Mass- and energy-separated Fission Fragments (FF) were provided by the ILL LOHENGRIN spectrometer, using thermal neutron-induced fission of ²³⁵U and ²³³U targets.
Polarization Mitigation: A voltage inversion procedure, or “cycling,” was implemented using a Keithley 6,487 supply to minimize polarization effects, particularly in pCVD and DOI detectors.
Timing Measurement: Timing resolution was determined by measuring the time difference between signals extracted from the two sides (0° and 180°) of a single detector using a 2 GHz, 40 dB broadband RF amplifier (CIVIDEC C2) and a 500 MHz, 3.2 GS s^-1 digital sampling system (“Wavecatcher”).
Spectroscopy Measurement: Energy resolution utilized a dedicated low-noise, fast-response charge sensitive preamplifier (INFN design) with a 0.5 µs Gaussian shaping time.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and custom engineering services required to replicate and extend the high-performance FF detection demonstrated in this research.

Applicable Materials

The superior timing and energy resolution achieved by the thin SCD detector (Detector B) make Optical Grade Single Crystal Diamond (SCD) the ideal material for high-fidelity FF detection.

6CCVD Material Recommendation	Specification Match	Customization Potential
Optical Grade SCD	Required for best energy (1.4% RMS) and timing (10.2 ps RMS) resolution.	6CCVD offers SCD thickness from 0.1 µm up to 500 µm, allowing precise tuning for optimal charge collection and PHD mitigation (e.g., replicating the high-performing 50 µm thickness).
Electronic Grade PCD	Suitable for large-area mosaics (up to 125mm) where high count rate capability is prioritized over ultimate energy resolution.	While pCVD showed poor CCE (30%), 6CCVD’s advanced PCD growth minimizes defects, offering large-area coverage up to 125 mm diameter for multi-detector arrays (as discussed for FIPPS integration).
Boron-Doped Diamond (BDD)	Alternative radiation-hard material for comparison or use as a neutron converter layer (e.g., ¹⁰B implantation, as used in the SiC detector).	6CCVD supplies BDD substrates and films, offering a diamond-based alternative to SiC for high-flux environments.

Customization Potential

The success of this research hinges on precise detector geometry and contact engineering, areas where 6CCVD provides comprehensive custom services:

Custom Dimensions and Mosaics: The paper discusses the need for large-area coverage (up to 2 cm² target area) potentially requiring a mosaic of detectors. 6CCVD supplies SCD and PCD plates up to 125 mm in diameter, enabling the fabrication of custom-sized detectors and multi-detector arrays.
Precision Thickness Control: The best energy resolution was achieved with a 50 µm SCD detector. 6CCVD guarantees SCD thickness control from 0.1 µm to 500 µm, essential for optimizing the electric field (V/µm) and minimizing the impact of the Pulse Height Defect (PHD).
Advanced Metalization Services: The experiment utilized complex metal stacks (DLC/Pt/Au, Ni/Ti, Al). 6CCVD offers in-house metalization capabilities including Au, Pt, Pd, Ti, W, and Cu, allowing researchers to test various Schottky or Ohmic contact schemes required for specific charge carrier collection (electron vs. hole).
Surface Quality: To minimize the “dead layer” effect noted in the paper (which caused a 3 MeV energy loss at the surface), 6CCVD provides ultra-smooth polishing for SCD (Ra < 1 nm) and inch-size PCD (Ra < 5 nm), ensuring minimal passive material traversal.

Engineering Support

6CCVD’s in-house PhD team specializes in optimizing MPCVD diamond for extreme environments and high-speed detection. We can assist researchers in material selection and design for similar Fission Fragment Detection and Time-of-Flight (TOF) projects, focusing on:

PHD Mitigation: Consulting on optimal detector thickness and bias voltage to maximize the electric field (V µm^-1) and reduce charge recombination in the Bragg peak region.
Timing Optimization: Designing ultra-thin SCD detectors and appropriate metalization layers to maintain the world-class timing resolution demonstrated (10.2 ps RMS).
Radiation Hardness: Providing materials certified for high-flux environments, ensuring long-term stability for in-beam experiments like FIPPS.

Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Experimental fission studies for reaction physics or nuclear spectroscopy can profit from fast, efficient, and radiation-resistant fission fragment (FF) detectors. When such experiments are performed in-beam in intense thermal neutron beams, additional constraints arise in terms of target-detector interface, beam-induced background, etc. Therefore, wide gap semi-conductor detectors were tested with the aim of developing innovative instrumentation for such applications. The detector characterization was performed with mass- and energy-separated fission fragment beams at the ILL (Institut Laue Langevin) LOHENGRIN spectrometer. Two single crystal diamonds, three polycrystalline and one diamond-on-iridium as well as a silicon carbide detector were characterized as solid state ionization chamber for FF detection. Timing measurements were performed with a 500-µm thick single crystal diamond detector read out by a broadband amplifier. A timing resolution of ∼10.2 ps RMS was obtained for FF with mass A = 98 at 90 MeV kinetic energy. Using a spectroscopic preamplifier developed at INFN-Milano, the energy resolution measured for the same FF was found to be slightly better for a ∼50-µm thin single crystal diamond detector (∼1.4% RMS) than for the 500-µm thick one (∼1.6% RMS), while a value of 3.4% RMS was obtained with the 400-µm silicon carbide detector. The Pulse Height Defect (PHD), which is significant in silicon detectors, was also investigated with the two single crystal diamond detectors. The comparison with results from α and triton measurements enabled us to conclude that PHD leads to ∼50% loss of the initial generated charge carriers for FF. In view of these results, a possible detector configuration and integration for in-beam experiments has been discussed.

Tech Support

Original Source

DOI: https://doi.org/10.3389/fphy.2021.732730

References

2017 - EXILL-a High-Efficiency, High-Resolution Setup for γ-spectroscopy at an Intense Cold Neutron Beam Facility [Crossref]
2020 - Development of a Liquid Scintillator Based Active Fission Target for FIPPS [Crossref]
2020 - Development of A Gas Filled Magnet for FIPPS Phase II [Crossref]
1976 - The Recoil Separator Lohengrin: Performance and Special Features for Experiments [Crossref]
2015 - Performance Study of an Integrated ΔE-E Silicon Detector Telescope Using the Lohengrin Fission Fragment Separator at ILL, Grenoble [Crossref]
1995 - Electronic Properties and Applications [Crossref]
2015 - Responsivity Study of Diamond X-ray Monitors with nUNCD Contact
2017 - Hétéroépitaxie de films de diamant sur Ir/SrTiO3/Si (001) : une voie prometteuse pour l’élargissement des substrats
2019 - Progress in Detector Properties of Heteroepitaxial diamond Grown by Chemical Vapor Deposition on Ir/YSZ/Si(001) Wafers [Crossref]
2021 - X-ray Beam Induced Current Analysis of CVD diamond Detectors in the Perspective of a Beam Tagging Hodoscope Development for Hadrontherapy On-Line Monitoring [Crossref]