Detector developments at DESY

At a Glance

Metadata	Details
Publication Date	2015-12-22
Journal	Journal of Synchrotron Radiation
Authors	C. Wunderer, A. Allahgholi, M. Bayer, Laura Bianco, Jonathan Correa
Institutions	Center for Free-Electron Laser Science, Elettra-Sincrotrone Trieste S.C.p.A.
Citations	7
Analysis	Full AI Review Included

6CCVD Technical Analysis: Diamond Detectors for Extreme Photon Environments

This documentation analyzes the key requirements derived from the DESY detector developments (AGIPD and PERCIVAL) and positions 6CCVD’s Chemical Vapor Deposition (CVD) diamond materials as the optimal solution for advancing high-flux, high-radiation detection systems in Free-Electron Lasers (FELs) and Synchrotrons.

Executive Summary

The development of advanced photon detectors (AGIPD and PERCIVAL) addresses the critical need for ultra-fast, high dynamic range imaging at modern X-ray facilities (Eu-XFEL, DESY). The core challenges and 6CCVD’s value proposition are summarized below:

Extreme Operating Environment: Detectors must manage multi-megahertz frame rates and survive cumulative radiation doses up to 1 GGy (Gigagray) over three years.
Performance Requirements: Necessity for single-photon sensitivity coupled with a high dynamic range (up to 10⁵ photons/pixel/frame) and minimal dead area.
Current Material Limitation: Current designs rely on silicon (Si) hybrid or CMOS monolithic sensors, which face inherent limits in radiation hardness and ultimate speed compared to diamond.
Diamond as the Solution: 6CCVD Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) offer vastly superior radiation hardness (up to 10⁴ times better than Si) and ultra-fast charge collection due to high carrier mobility (ideal for MHz/GHz timing applications).
Custom Sensor Prototyping: 6CCVD provides custom, high-purity MPCVD diamond wafers (SCD and PCD) in required dimensions (up to 125mm) and custom metalization schemes (Ti/Pt/Au) necessary for robust Schottky diode or p-i-n radiation detector fabrication.
Replication and Extension: Utilizing 6CCVD materials enables researchers to bypass the radiation limits of silicon, providing a path to maintenance-free, permanent detector components for the most intense beamlines.

Technical Specifications

The following hard parameters define the performance envelope required by the AGIPD and PERCIVAL detectors, highlighting the extreme operating conditions appropriate for diamond solutions.

Parameter	Value	Unit	Context
AGIPD Maximum Frame Rate	4.5	MHz	Within XFEL bunch train (2700 pulses)
AGIPD Target Dynamic Range	Single photon to 10⁴	photons	Per pixel at 12 keV
AGIPD Pixel Pitch	200	µm	Full-size chip design (AGIPD1.0)
AGIPD Sensor Thickness	500	µm	Standard silicon sensor thickness
AGIPD Radiation Tolerance Target	Up to 1	GGy	Expected total dose over 3 years
PERCIVAL Sensor Size (13M version)	10 x 10	cm	Large monolithic sensor
PERCIVAL Maximum Frame Rate	120	Hz	Full operating speed (Commensurate with most FELs)
PERCIVAL Dynamic Range	1 to 10⁵	photons	Per pixel, per frame (500 eV)
PERCIVAL Energy Range (Primary)	250 eV to 1	keV	Soft X-ray regime
PERCIVAL Pixel Pitch	27	µm	Small pixel requirement
PERCIVAL Output Data Rate (13M)	~50	Gbit s^-1	Full speed output requirement

Key Methodologies

The detector architectures presented demand specialized material processing and integration techniques, many of which directly leverage 6CCVD’s fabrication expertise.

Detector Architecture:
- AGIPD: Hybrid pixel technology utilizing a discrete sensor bump-bonded to a read-out ASIC (Application-Specific Integrated Circuit).
- PERCIVAL: Monolithic Active-Pixel Sensor (MAPS) based on CMOS technology, integrating the sensor and readout circuitry on a single substrate.
Dynamic Range Management:
- Adaptive Gain Switching: Achieved via integrated control logic, a discriminator, and switchable capacitors (C2, C3) placed in parallel to the Charge-Sensitive Pre-Amplifier (CSA). This allows automatic, per-pixel, per-frame adjustment across three gains to cover a 5-decade dynamic range.
High-Speed Imaging:
- On-Chip Storage: AGIPD utilizes 352 analog memory cells per pixel to store images from fast pulse trains (4.5 MHz).
Soft X-ray Optimization:
- Backside Illumination (BSI) Processing: PERCIVAL sensors require back-thinned and back-processed silicon for optimal Quantum Efficiency (QE) and uniform response in the sub-keV soft X-ray range. This processing step must minimize contaminants to ensure uniformity and efficiency.
Readout and Data Handling:
- PERCIVAL features on-chip ADCs converting signals to 12 ADC bits + 2 gain bits, with data output via 111 LVDS lines at ~480 MHz.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced diamond materials required to replicate or enhance the radiation and speed characteristics of the AGIPD and PERCIVAL projects, providing a direct pathway for research in ultra-hard and ultra-fast detection.

Applicable Materials for FEL and Synchrotron Detection

Material Grade	Description & Application	6CCVD Capability Match
High-Purity Single Crystal Diamond (SCD)	Ideal for high-speed, ultra-radiation-hard particle and photon counting detectors (e.g., SCD Schottky detectors). Meets the extreme speed requirements of 4.5 MHz AGIPD pulsing.	SCD Substrates: Thicknesses from 0.1 µm to 500 µm, with Ra < 1 nm polished surface quality for superior metal contacts.
Semi-Insulating Polycrystalline Diamond (PCD)	Suitable for large-area detectors and X-ray beam monitors where sensors need to match or exceed the 10 cm x 10 cm dimension of the PERCIVAL 13M design.	Large Area PCD: Wafers/plates up to 125 mm in diameter, enabling fabrication of multi-megapixel or large-area diagnostic arrays.
Boron-Doped Diamond (BDD)	Used for Ohmic or p-type contacts in p-i-n diamond radiation detectors or high-performance electrodes.	BDD Films: Controlled doping levels available for application-specific conductivity requirements.

Customization Potential for Detector Replication

6CCVD offers specialized engineering services to meet the exacting physical and electrical requirements of high-performance photon detectors:

Large-Area Fabrication: The PERCIVAL 13M sensor targets 10 cm x 10 cm. 6CCVD can supply inch-size PCD wafers up to 125 mm, which are ideal candidates for scale-up studies in extremely radiation-hard detector materials.
Thickness Control: 6CCVD can match the 500 µm sensor thickness used in the AGIPD design for both SCD and PCD materials, ensuring direct compatibility for bump-bonding studies.
Custom Metalization & Electrode Definition: Diamond detectors require high-quality metal electrodes for biasing and signal collection (Schottky and Ohmic contacts). 6CCVD provides in-house thin-film deposition services crucial for prototyping:
- Metals Available: Au, Pt, Pd, Ti, W, Cu.
- Processing: Custom patterning via photolithography and laser cutting to define pixel structures (e.g., 27 µm or 200 µm pitch requirements).
Surface Preparation: Polishing services ensure the required electrical stability and optimal material interface, achieving Ra < 1 nm (SCD) and Ra < 5 nm (PCD) finishes.

Engineering Support & Logistics

6CCVD’s in-house PhD team can assist with material selection for similar XFEL/Synchrotron high-flux detection and beam monitoring projects, specializing in optimizing diamond growth parameters (purity, defect density, grain size) to maximize charge collection efficiency (CCE) and minimize polarization effects common in high-flux diamond detectors.

We ensure robust logistics, offering Global Shipping (DDU default, DDP available) to research institutions worldwide, including those collaborating on DESY-led projects (e.g., RAL/STFC, PSI, Elettra Sincrotrone).

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

View Original Abstract

With the increased brilliance of state-of-the-art synchrotron radiation sources and the advent of free-electron lasers (FELs) enabling revolutionary science with EUV to X-ray photons comes an urgent need for suitable photon imaging detectors. Requirements include high frame rates, very large dynamic range, single-photon sensitivity with low probability of false positives and (multi)-megapixels. At DESY, one ongoing development project - in collaboration with RAL/STFC, Elettra Sincrotrone Trieste, Diamond, and Pohang Accelerator Laboratory - is the CMOS-based soft X-ray imager PERCIVAL. PERCIVAL is a monolithic active-pixel sensor back-thinned to access its primary energy range of 250 eV to 1 keV with target efficiencies above 90%. According to preliminary specifications, the roughly 10 cm × 10 cm, 3.5k × 3.7k monolithic sensor will operate at frame rates up to 120 Hz (commensurate with most FELs) and use multiple gains within 27 µm pixels to measure 1 to ∼100000 (500 eV) simultaneously arriving photons. DESY is also leading the development of the AGIPD, a high-speed detector based on hybrid pixel technology intended for use at the European XFEL. This system is being developed in collaboration with PSI, University of Hamburg, and University of Bonn. The AGIPD allows single-pulse imaging at 4.5 MHz frame rate into a 352-frame buffer, with a dynamic range allowing single-photon detection and detection of more than 10000 photons at 12.4 keV in the same image. Modules of 65k pixels each are configured to make up (multi)megapixel cameras. This review describes the AGIPD and the PERCIVAL concepts and systems, including some recent results and a summary of their current status. It also gives a short overview over other FEL-relevant developments where the Photon Science Detector Group at DESY is involved.

Tech Support

Original Source

DOI: https://doi.org/10.1107/s1600577515022237