RF pulse amplifier for CVD-diamond particle detectors

At a Glance

Metadata	Details
Publication Date	2021-04-01
Journal	Journal of Instrumentation
Authors	C. Hoarau, G. Bosson, J.-L. Bouly, S. Curtoni, D. Dauvergne
Institutions	Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble Alpes
Citations	10
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Speed CVD Diamond Detectors for Hadron Therapy

Executive Summary

This research details the development of an ultra-low power, high-speed Low Noise Amplifier (LNA) specifically designed for Chemical Vapor Deposition (CVD) diamond particle detectors used in hadron therapy beam monitoring.

Application Focus: High-frequency pulsed particle beam monitoring and time-stamping in hadron therapy, requiring sub-nanosecond timing resolution.
Performance Achieved: The LNA demonstrates exceptional speed (350 ps rise time) and timing stability (minimum jitter of 43 ps), essential for preserving the high mobility characteristics of diamond.
Ultra-Low Power: The design achieves a power consumption of only 72-75 mW per channel, enabling the integration of multi-channel readout (up to 40 strips) necessary for large-area, striped diamond hodoscope designs.
Material Requirements: The project utilizes both large-area Polycrystalline CVD (pCVD) (20 x 20 mm²) and high-purity Single Crystal CVD (sCVD) (4.5 x 4.5 mm² mosaic) sensors, ranging in thickness from 300 µm to 500 µm.
6CCVD Value Proposition: 6CCVD specializes in providing the high-purity SCD and large-area PCD substrates, custom cut to precise dimensions, and equipped with application-specific metalization (e.g., strip electrodes) required to replicate and scale this advanced detector technology.

Technical Specifications

The following hard data points were extracted from the analysis of the LNA performance and detector requirements:

Parameter	Value	Unit	Context
LNA Gain (Maximum)	46	dB	Measured at 10 MHz
LNA Gain (High Frequency)	31	dB	Measured at 2 GHz
LNA Power Consumption	72 - 75	mW	Total power per channel
Output Pulse Rise Time (T_20/80)	350	ps	Simulation and measurement
Minimum Jitter	43	ps	Measured at 25% trigger level
Equivalent Noise Charge (ENC)	230	e	Estimated
SCD Thickness (Tested)	500	µm	Used for ²⁴¹Am source testing
PCD Prototype Dimensions	20 x 20	mm²	300 µm thickness
SCD Mosaic Dimensions	4.5 x 4.5	mm²	500 µm thickness (4 crystals)
Applied Electric Field (Typical)	1	V/µm	Required for charge carrier drift
Detector Bias Voltage (Tested)	500	V	Applied across 500 µm SCD
Electrode Thickness (Tested)	100	nm	Aluminum (Al) electrodes

Key Methodologies

The following steps outline the critical material and electronic methodologies used to achieve the high-performance diamond detector system:

Detector Material Selection: Two primary diamond types were utilized: large-area Polycrystalline CVD (pCVD) for initial prototypes and high-purity Single Crystal CVD (sCVD) crystals arranged in a mosaic for the final hodoscope design.
Custom Dimensions: SCD crystals were prepared at 4.5 x 4.5 mm² and 500 µm thickness, while pCVD plates were 20 x 20 mm² and 300 µm thick.
Electrode Fabrication: Detectors were metalized with 100 nm thick Aluminum (Al) electrodes. The final hodoscope design requires double-side strip metalization, fabricated using a lift-off process for particle localization.
LNA Design: A two-stage, surface-mount device (SMD) architecture was employed to minimize parasitic effects and control costs, utilizing RF layout techniques for high-frequency performance.
Active Components: The first stage used a wideband NPN RF Si-Ge Heterojunction Bipolar Transistor (HBT) (Infineon BFP740, F_T ~39 GHz) for low noise and timing constraints. The second stage used an integrated Low Noise Amplifier (Infineon BGA427).
High Voltage Biasing: The detector was biased at high voltage (e.g., 500 V) via a T-shaped low-pass filter. The PCB layout ensured a 3 mm spacing between the high voltage line and ground to prevent sparking.
Performance Validation: Time domain measurements were conducted using a calibrated pulse generator and a ²⁴¹Am alpha source coupled to the 500 µm SCD detector, confirming the 350 ps rise time and low jitter performance.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced CVD diamond materials and customization services required to replicate, scale, and extend this high-performance particle detection research.

Applicable Materials

Research Requirement	6CCVD Material Solution	Technical Advantage
High-Purity SCD (500 µm)	Optical Grade Single Crystal Diamond (SCD)	Ultra-low defect density ensures maximum charge collection efficiency (CCE) and preserves the intrinsic high mobility (2064 cm².V^-1.s^-1) required for sub-nanosecond timing.
Large-Area PCD (20 x 20 mm²)	High-Quality Polycrystalline Diamond (PCD)	Available in plates up to 125 mm diameter, easily meeting the 20 x 20 mm² requirement for large-area beam monitoring prototypes.
Detector Thickness (300 µm - 500 µm)	Custom Thickness Wafers	6CCVD offers precise thickness control for both SCD and PCD from 0.1 µm up to 500 µm, ensuring optimal charge collection depth for specific particle energies (e.g., 5.5 MeV alpha particles).

Customization Potential

The success of the diamond hodoscope relies on precise material preparation and electrode patterning, areas where 6CCVD provides comprehensive in-house services:

Custom Dimensions and Mosaics: The paper requires small 4.5 x 4.5 mm² SCD crystals. 6CCVD provides precision laser cutting to produce custom-sized plates and wafers, facilitating the assembly of complex mosaic detectors for large-area coverage.
Strip Metalization: The final design requires double-sided strip electrodes for particle localization. 6CCVD offers internal metalization capabilities including Au, Pt, Pd, Ti, W, and Cu. We can tailor the metal stack and thickness (e.g., replacing the 100 nm Al with a robust Ti/Pt/Au stack) and utilize advanced lithography techniques to define the high-resolution strip patterns required for the hodoscope.
Surface Finish: To ensure optimal electrode adhesion and minimize surface leakage current under high bias (500 V), 6CCVD guarantees ultra-smooth polishing with surface roughness (Ra) less than 1 nm for SCD and less than 5 nm for inch-size PCD.

Engineering Support

The development of fast electronics for diamond detectors in High Energy Physics (HEP) and medical physics (hadron therapy) requires deep material expertise. 6CCVD’s in-house PhD engineering team specializes in optimizing CVD diamond properties for high-speed, high-radiation environments. We can assist researchers in selecting the ideal material grade, thickness, and metalization scheme to maximize Charge Collection Efficiency (CCE) and minimize timing jitter for similar Hadron Therapy Beam Monitoring projects.

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

View Original Abstract

Abstract This article introduces a design of a Low Noise Amplifier (LNA), for the field of diamond particle detectors. This amplifier is described from simulation to measurements, which include pulses from α particles detection. In hadron therapy, with high-frequency pulsed particle beams, the diamond detector is a promising candidate for beam monitoring and time-stamping, with prerequisite of fast electronics. The LNA is designed with surface mounted components and RF layout techniques to control costs and to allow timing performance suitable for sub-nanosecond edges of pulses. Also this amplifier offers the possibility of high voltage biasing, a characteristic essential for driving diamond detectors. Finally the greatest asset of this study is certainly the minimization of the power consumption, which allows us to consider designs with multiple amplifiers, in limited space, for striped diamond detectors.

Tech Support

Original Source

DOI: https://doi.org/10.1088/1748-0221/16/04/t04005

References

1980 - A SILICON SURFACE BARRIER MICROSTRIP DETECTOR DESIGNED FOR HIGH-ENERGY PHYSICS [Crossref]
1991 - CMOS low noise amplifier for microstrip readout: Design and results [Crossref]