Practical Applications of CVD Diamond Detectors DDL : Kevin Oliver

Practical Applications of CVD Diamond Detectors DDL : Kevin Oliver

Acknowledgements Element Six (Helen Murphy, Neil Perkins, Andrew Whitehead) RD42 (Harris Kagan, William Trischuk, Peter Weilhammer, Steve Schnetzer, Bob Stone) GSI/Nordhia (Eleni Berdermann) ESRF (John Morse) CEA (Phillipe Bergonzo) Scanditronix (Camilla Ronnqvist) Los Alamos National Laboratory CERN Fermilab Diamond Light Source/ Daresbury and many others. June 30, 2023 2

Outline What makes diamond a good detector? What can be detected by diamond? Diamond detector timeline Different types of diamond and its uses in different applications Application of polycrystalline diamond: the Atlas Experiment Application of single crystal CVD diamond: X-ray dosimetry Fluorescence Detectors & Diamond Light Source Making diamond detectors available – Diamond Detectors Ltd June 30, 2023 3

What makes diamond a good detector? Intrinsic Properties Low Z (tissue equivalent) Low absorption High thermal conductivity Radiation Hardness Wide band gap (no thermally generated noise) High product grades available (of same order as for GaAs) Detector Properties High sensitivity (application dependent) Good spatial and temporal resolution achievable Low (and stable) noise Low capacitance Device Advantages Intrinsically simple device can fabricate robust, compact devices High temperature operation (no need for cooling) June 30, 2023 4

What can be detected by diamond? a) Charged particles e.g. Alpha, Beta, high energy ions b) Neutral particles for which diamond has a sufficiently high reaction cross-section e.g. neutrons with energies above 5.8MeV c) Particles which can be converted into charged particles that can be detected by diamond e.g. thermal neutrons d) Photons with energy 5.5eV i.e. UV, X-ray and gamma rays June 30, 2023 5

Diamond Detector Timeline Natural Diamond 1920’s 1940’s 1950’s 1960’s 1962 1970’s 1980’s Naturals demonstrate UV response. Naturals used to detect ionising nuclear radiation Interactions of Alpha and high energy fast electrons with diamond studied Photoconductivity of naturals investigated Advances made in forming electrical contacts to diamond Commercial xray dosimeters for medical applications. Polycrystalline CVD early 1990’s Advances made in quality of polycrystalline CVD diamond Diamond late 1990’s Suggested use of pCVD in Super Conducting Super Collider. Commercial solar blind UV detector. Beam position monitors for synchrotrons Charge Collection distance 200 microns achieved suitable for high energy physics detector applications. Single Crystal CVD Diamond 2000’s June 30, 2023 High purity single crystal CVD diamond with superior electronic characteristics. 6

Diamond Detector Applications A wide range of detector applications and detector types make diverse demands on the material Particle physics: beam condition monitors, trackers, beam abort systems Dosimetry: radiation therapy, equipment calibration, active exposure monitoring Nuclear applications: homeland security, nuclear reactors and fusion experiments Synchrotrons: white beam monitoring UV detectors: photolithography ,flame detection and solar physics Alpha/Beta: air-Flow and survey meters, waste incineration June 30, 2023

Diamond Particle Detectors High Energy Particle Physics: at CERN, BaBar, CDF etc - solid state ionisation chambers- pixel, strip and dot detectors - fluorescence detectors (e.g. RD42) Heavy Ions: start detectors and spectroscopy (e.g. GSI and the Nordhia collaboration) Neutron detection: nuclear industry, research and dosimetry -Thermal neutrons: fluence and profile monitoring for nuclear reactors (e.g. Bergonzo et al, CEA) -Fission neutrons : nuclear reactors (e.g. Schmid et al, Los Alamos) -Fusion: Tokamaks (e.g. ITER) Alpha and Beta detection: - Energy resolution approaching that of silicon reported for high purity single diamond irradiated with Am-241. June 30, 2023 8

Diamond Photon Detectors Active Dosimetry : solid state ionisation chambers detecting x-rays or hadrons (e.g. MAESTRO – “Methods and Advanced Equipment for Simulation and Treatment in Radiation Oncology” – EU funded project with a workpackage on diamond dosimetry Synchotrons: solid state ionisation chambers and fluorescence detectors continuous monitoring of white beams Fluorescence detectors: work in progress for DLS (new UK synchrotron) NSCL at MSU utilising hetero-epitaxial diamond ESRF UV detection: deep UV detectors. Variety of applications for robust UV sensors that can survive harsh environment e.g. Photolithography, Solar Physics (European Space Agency) (e.g. Pace et al, Jackman et al) June 30, 2023 9

Natural Diamond (ND) Detectors ND detectors are made from highly selected natural stones Applications include: dosimetry for use in medical physics and for calibration detecting proton spectra close to deuterium plasmas detecting high energy heavy ion spectra solar blind UV detectors Cost and availability: only 1% of all diamonds are type IIa a very small fraction of the 1% will ever make a useful detector. - You need to sort through many, many stones . Even with extreme selection, the performance of ND detectors varies from one diamond to another Typical cost 2K June 30, 2023 10

Choice of CVD Diamond Grade/Type Differing types/grades of CVD diamond - very different properties Selection based on desired detector performance, considering: Key Considerations Detector type Charge Collection Distance (CCD) Detector Area Fast decay time Operating voltage Low leakage through bulk Minimum beam perturbation Flourescence Opacity June 30, 2023 11

Electronic grades of CVD diamond Intrinsic Polycrystalline Intrinsic single crystal µe 1800 cm2/Vs µh 1000 cm2/Vs VBD 0.5 MV/cm µe 4500 cm2/Vs µh 3800 cm2/Vs VBD 4 MV/cm CCD 250 µm at 1 V/µm field CCD is thickness limited 12

EL Polycrystalline CVD Diamond (E6) Developed for use in HEP experiments Charge collection efficiency at 1V/ m: 40% Charge Collection Distance at 1V/ m: m - Low nitrogen content - Large grains High breakdown voltage - Low sp2 incorporation June 30, 2023

Polycrystalline Diamond Detectors Diverse requirements for Beam Condition Monitoring in high energy particle physics Single particle counting Example: ATLAS @ CERN, Switzerland June 30, 2023 Particle flux measurement Examples: Babar @ Stanford, USA Belle @ KEK, JAPAN CDF @ Fermilab, USA 14

Flux Measurement at CDF The Collider at Fermilab (CDF) 2 pCVD diamond detectors since 2004 Their performance paved the way for the ATLAS BCM. Now has 13 pCVD diamonds : 8 inside and 5 more outside near the existing beam loss monitor (BLM). A BLM monitors the beam and will shut it down if it detects a problem. June 30, 2023 15

Beam Incident at CDF Diamond detectors Abort Signal from IC BLM (IC) During a beam Incident (November 2006): Diamond detectors and ionisation chambers were monitoring the beam Diamond responded quicker Diamond detectors now being commissioned. June 30, 2023 16

Single Event Detection at ATLAS : The ATLAS Beam Conditions Monitor (BCM) Time of flight measurement to distinguish collisions from background Tracking devices close to interaction region Single particle counting Requires low noise and fast readout High precision tracking Allows timing correlations Must survive harsh environment for 10 years June 30, 2023 17

ATLAS Detector, CERN June 30, 2023 18

Large EL Polycrystalline Pixel Detector 64x19mm Pixel detector 45000 pixels Pitch 50 x 400 microns Resolution pitch/ 12 Particle beam intensity map taken at Large Hadron Collider, CERN June 30, 2023 20

Radiation Hardness : Polycrystalline Diamond Proton Irradiation of EL Poly Tracker ATLAS detectors must withstand 50 Mrad over 10 years Accelerated test 1.8 x 1016 p/cm2 500Mrad 24 GeV protons Blue E 1V/ m Green E 2 V/ m June 30, 2023 21

Fluorescence Detector for Diamond Light Source Diamond Light Source (DLS) is a new synchrotron at Harwell, UK A range of different poly CVD diamond grades are being evaluated for use as a large area fluorescence detector at DLS Why a diamond detector for the synchrotron? Excellent Thermal Conductivity- can withstand heat-load of white beam Therefore can provide continuous white beam monitoring - unique! Excellent Mechanical Stability- can provide a vacuum barrier. Therefore can act as window and beam position monitor Low absorption of X-ray and visible light Can be brazed or diffusion bonded Thin samples allow attainment of higher spatial resolution due to the focal plane of the imaging camera June 30, 2023 22

Fluorescence Detector for Diamond Light Source Preliminary results from Drakopoulos et al at Daresbury, UK: EL PCVDD Grade Standard PCVDD Grade Images of visible light fluorescence excited by 10 keV x-ray radiation Relative Luminescence Yield per deposited power Comments EL PCVD D 1423 Most uniform luminescence Optical grade 1177 Standard grade 397 June 30, 2023 Less uniform luminescence Speckle - unsuitable 23

Single Crystal CVD Diamond Detectors High purity electronic grade SC CVDD: High charge collection efficiency (approaching 100%) High mobilities High spatial resolution High energy resolution High sensitivity in some applications Lower saturation field (0.2 V/ m). Low energy and angular dependence (Xray) Radiation hard June 30, 2023 24

Diamond Dosimetry in Radiation Therapy Intensity Modulated Radiation Therapy (IMRT): a new technique for cancer treatment driving improvements in dosimetry Scanditronix Wellhöfer (SW) provide high-end dosimetry equipment for use in hospitals and industry across the world. IMRT demands high spatial resolution. Arrays are desirable to speed up the mapping process. Commercial production of SC detector material is allowing SW to switch from silicon detectors and ionisation-chambers to synthetic diamond. June 30, 2023 25

Example Application of EL SC CVD Diamond: Focussed Photon Beam Profile Intensity Modulated Radiation Therapy Before treatment of patient: Dummy run with detector Detector placed in tissue equivalent material to assess beam profile Detector must be moved several times to collect enough information - an array of detectors would be ideal Courtesy of Scanditronix June 30, 2023 Treatment: Patient typically receives 3 treatments, each from a different angle of entry 26

X-ray Sensitivity for Different Diamond Types Sample Type Dose Rate (Gy/min) Signal (nC/Gy/mm3) Priming (Gy) 0.5 308 0 E6 Standard purity SC CVDD 2 26 3 Commercially available natural diamond dosimeter 2 48 8 E6 High Purity SC CVDD Data for samples irradiated with 5MV X-ray beam courtesy of Scanditronix High Purity SC CVD diamond gave 6x signal of commercially available natural diamond dosimeter June 30, 2023 27

X-ray Sensitivity Comparison for Different Dosimeter Types Higher sensitivity of High Purity SC CVDD Smaller devices Improved spatial resolution E6 HP SC CVD diamond Commercial Silicon dosimeter Air-filled Ionisation chamber Sensitivity (nC/Gy) 240 74 7.5 Active Detector Volume (mm3) 0.3 0.2 120 Data for samples irradiated in a 6MV photon beam with a 10cm x 10cm field at a source-to-detector distance of 100cm, courtesy of Scanditronix June 30, 2023 28

Tailoring Diamond for Applications June 30, 2023 29

Overview A diamond detector is an intrinsically simple device BUT Its performance is critically dependent on: Surface preparation Edge preparation Metallisation Packaging These activities need to be bespoke to each application and potentially to each customer. June 30, 2023 30

Diamond Detectors Ltd (DDL) Why DDL was created? The focus of Element Six Ltd is on material development and bulk material synthesis. The detector market requires a diverse range of engineered products and skills. Including development, manufacture and sales. DDL has been formed to provide market focus and develop a range of packaged devices. To provide research and industry with a partner capable of providing the added processes needed to take diamond from material to characterised detector. DDL was formed in February 2007, and now consists of a small experienced team. June 30, 2023 31

DDL – Providing Detectors Diamond Synthesis Element Six DDL Material Processing Die Fabrication and Test Die/Wire Bonding. Packaging Characterisation. Packaged Solutions to Customers in R&D and Industry June 30, 2023 Market Driven Requirements or Specification

DDL – Roadmap – 2007/08 Phase-I (2007 - Q3) - Technology Transfer from E6 to DDL (Completed) - Build Start (access to premises from 2nd June 2007) Phase-II (2007 - Q4) -Fabrication and packaging of simple devices - Build Completion. Phase-III (2008) -Fabrication and packaging of more complex devices Clean Room Assembly Lithography Laser Room June 30, 2023 Chemical Lab 33

DDL- Markets HEP :- High Energy Physics Community. X-rays :- Medical/Health Physics (High Flux Applications) UV ( 220nm) :- Photolithography, Flame, Military Application Neutrons :- Reactor Monitoring, Military Dosimeters, Well logging Alpha /Beta :- Air Flow, Nuclear Waste Incineration, Military. High energy particle To charge measurement system e- Bias h Electrodes CVD diamond 34

DDL – Target Market Example Neutron Detection Neutrons “Well Logging & Reactor Monitoring” Logging companies have confirmed interest/merit in replacing 3 He tubes. Logging while drilling is more important in deeper wells and in modern technologies like horizontal drilling. Current solutions last 1 - 6 hours in this harsh high temperature/pressure environment. In 2001 there were 2018 rotary rigs operations world wide. June 30, 2023 35

Material Summary From early experiments using naturals, diamond detectors have now grown into diverse applications with substantial commercial opportunities. CVD diamond provides consistent performance, and is much more available than natural diamond The grade of CVD diamond, including whether it is SC or poly, needs selecting according to application. June 30, 2023 36

Market Summary New markets are being opened up by improved material quality, larger available sizes, and an increased understanding of diamond performance New diamond detector applications are being driven by technological advances in other fields e.g. radiation therapy In exploitation of diamond detectors careful device fabrication is essential A new detector company, Diamond Devices Ltd, has been set up to service these markets June 30, 2023 37

The End Thank you June 30, 2023 38

CVD-SC Diamond Characteristics Impact Si GaAs 4H SiC GaN Diamond Units Pout (Vmax) R, ft, Pout(Imax) 0.31 0,48 3 5 20 MV/cm 1450 8600 900 2000 4500 cm2/Vs Hole Mobility R, ft, Pout(Imax) 480 130 120 200 3800 cm2/Vs Saturation Velocity ft 0.86 0.72 2 2.5 2.7 107 cm/s Thermal Conductivity Pout(T), ft (T) 1.5 0.46 5 1.3 24 W/cmK Max. Electric Field Electron Mobility Comparison of material properties [R : series resistance, ft current gain cut-off frequency, Imax maximum current density, Vmax : maximum bias voltage, Pout maximum output power] 39

Single particle detection with a risetime less than 300ps and the (1/e-) falltime is 1ns June 30, 2023 From paper Diamond for Subnanosecond time resolution GSI 40

Choice of CVD Diamond Grade/Type Differing types/grades of CVD diamond - very different properties Selection based on desired detector performance, considering: Key Considerations Material Selection Detector type Ionisation Chamber style, Thermoluminescence, Charge Collection Distance (CCD) 200 m for high quality thick poly 100% efficiency for high purity single crystal. (CCD determined by sample thickness) Detector Area Polycrystalline material: up to 140 mm diameter Single crystal: up to 5 x 5 mm pieces available in volume – can be tiled Fast decay time Select material containing sufficient traps, or If high CCD also required: Thin high quality single crystal Operating voltage Polycrystalline material: high quality poly enables device operation at up to 2 V/ m. (In poly, ccd varies linearly with applied field). High purity single crystal: enables lower operating voltages (ccd saturates at 0.2 V/ m) Low leakage through bulk High quality poly High purity single crystal Minimum beam perturbation Thin high purity single crystal of high crystalline quality, Flourescence Select grade to give desired level of fluorescence and absence of speckle Opacity Do you want visible light to pass through, such as laser light? June 30, 2023 41