Properties of temporal X-ray in nanosecond-pulse discharges with a tube-to-plane gap at atmospheric pressure
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-01-01 |
| Journal | Acta Physica Sinica |
| Authors | Hou X, Cheng Zhang, Jintao Qiu, Jianwei Gu, Ruixue Wang |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Nanosecond X-ray Detection using MPCVD Diamond
Section titled âTechnical Documentation & Analysis: Nanosecond X-ray Detection using MPCVD DiamondâExecutive Summary
Section titled âExecutive SummaryâThis research validates the use of high-ppurity diamond photoconductive detectors (PCDs) for ultra-fast X-ray diagnostics in high-power pulsed gas discharge systems. 6CCVD specializes in the custom fabrication of the core material required for this advanced application.
- Application Focus: Investigation of runaway electron dynamics and bremsstrahlung X-ray generation in atmospheric nanosecond-pulse discharges.
- Critical Material Validation: High-purity, Type II-a Single Crystal Diamond (SCD) was successfully employed as the photoconductive detector element, demonstrating superior speed.
- Ultra-Fast Response: The PCD measured X-ray pulses with an extremely rapid rise time of approximately 1 ns and a pulse width of 2 ns, confirming diamondâs suitability for high-speed diagnostics.
- Energy Measurement: Typical calculated X-ray energy was 2.3 x 10-3 J per pulse at a peak voltage of -120 kV.
- Key Findings: X-ray intensity is inversely proportional to the inter-electrode gap and decreases linearly with increasing anode foil thickness, confirming X-ray generation primarily occurs at the anode surface.
- 6CCVD Value Proposition: We provide custom-dimensioned, high-purity SCD and specialized metalization services necessary to replicate and advance these high-speed radiation detectors.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental setup and results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Applied Peak Voltage | -120 | kV | Nanosecond pulse power supply |
| Power Supply Rise Time | 1.2 - 1.6 | ns | VPG-30-200 specification |
| Measured X-ray Rise Time | ~1 | ns | Detected by PCD |
| Measured X-ray Pulse Width | ~2 | ns | Detected by PCD |
| Calculated X-ray Energy (Typical) | 2.3 x 10-3 | J | Per pulse calculation |
| Inter-Electrode Gap (Tested Range) | 45 - 55 | mm | Tube-to-plane geometry |
| Anode Foil Thickness (Tested Range) | 20, 40, 60, 80 | ”m | Layered aluminum foil |
| PCD Material Type | II-a | N/A | High-purity Single Crystal Diamond (SCD) |
| PCD Detector Thickness | 1 | mm | Detector element dimension |
| PCD Bias Voltage | 100 | V | DC bias |
| PCD Sensitivity (S) | 3 x 10-4 | A/W | In 0.1-5.0 keV photon energy range |
| Operating Pressure | 96 | kPa | Atmospheric air (20 °C) |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized a specialized nanosecond-pulse power supply and a custom discharge chamber to generate and analyze X-ray emissions.
- Discharge Generation: Nanosecond-pulse discharge was initiated in atmospheric air (96 kPa) using a tube-to-plane electrode configuration, driven by a VPG-30-200 power supply (0-200 kV, 3-5 ns FWHM).
- Detector Selection: A commercial Diamond Photoconductive Detector (PCD) was selected, featuring a 3 mm x 1 mm, 1 mm thick, Type II-a SCD element.
- PCD Circuitry: The PCD was integrated into a measurement circuit consisting of a 100 V DC bias, a charging capacitor (C), and a signal resistor (R0 = 50 Ω), matched to the coaxial cable impedance to prevent reflection.
- Measurement Positions: X-ray signals were recorded simultaneously at two locations: (a) the side of the discharge chamber (measuring total emission) and (b) directly behind the aluminum foil anode (measuring transmitted bremsstrahlung).
- Parameter Variation: The inter-electrode gap was systematically adjusted from 45 mm to 55 mm, and the anode thickness was varied by stacking 20 ”m aluminum foils (up to 80 ”m total).
- Data Acquisition: Signals were captured using a high-bandwidth (2 GHz) oscilloscope (LeCroy Waverunner 204 Xi) at a 10 GS/s sampling rate to resolve the nanosecond-scale pulses.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful detection of ultra-fast X-ray pulses relies entirely on the high purity and electronic properties of the diamond material used. 6CCVD is uniquely positioned to supply and customize the SCD required for this demanding research field.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this research into higher energy or higher flux regimes, researchers require the highest quality SCD material, equivalent to the II-a type used in the paper.
| 6CCVD Material | Specification | Application Relevance |
|---|---|---|
| Optical Grade SCD | High purity, low nitrogen content (equivalent to Type II-a). Ra < 1 nm polishing available. | Essential for high carrier mobility and fast response time (< 1 ns) required for nanosecond pulse detection. |
| Custom SCD Substrates | Thicknesses from 0.1 ”m up to 500 ”m (wafers) or up to 10 mm (substrates). | Allows researchers to optimize detector volume and absorption depth for specific X-ray energy ranges (e.g., optimizing for keV vs. MeV photons). |
| Polycrystalline Diamond (PCD) | Plates up to 125 mm diameter, Ra < 5 nm polishing. | Suitable for large-area detectors or applications where cost-efficiency is prioritized over ultimate speed/purity. |
Customization Potential
Section titled âCustomization PotentialâThe paper utilized a specific 3 mm x 1 mm detector element. 6CCVD offers comprehensive customization services to meet precise experimental requirements.
- Custom Dimensions and Shaping: 6CCVD provides precision laser cutting and machining services to produce SCD and PCD plates in custom sizes and geometries (e.g., 3 mm x 1 mm elements, or larger inch-size wafers up to 125 mm).
- Advanced Metalization: Reliable ohmic contacts are crucial for PCD performance. We offer in-house metalization using standard stacks (e.g., Ti/Pt/Au) or custom materials (W, Cu, Pd) optimized for high-voltage biasing and minimal signal distortion in pulsed environments.
- Surface Finish: We guarantee ultra-smooth surfaces (Ra < 1 nm for SCD) which is vital for achieving uniform electric fields and reliable contact interfaces, maximizing detector efficiency and stability.
Engineering Support
Section titled âEngineering SupportâThe physics of runaway electron beams and high-power pulsed plasma requires specialized material knowledge.
- Expert Consultation: 6CCVDâs in-house PhD engineering team provides authoritative support for material selection, detector design, and optimization for high-power pulsed plasma and radiation detection projects.
- Global Logistics: We ensure reliable global shipping (DDU default, DDP available) for time-sensitive research projects, minimizing downtime.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Nanosecond-pulse discharge can produce low-temperature plasma with high electron energy and power density in atmospheric air, thus it has been widely used in the fields of biomedical science, surface treatment, chemical deposition, flow control, plasma combustion and gas diode. However, some phenomena in nanosecond-pulse discharge cannot be explained by traditional discharge theories (Townsend theory and streamer theory), thus the mechanism of pulsed gas discharge based on runaway breakdown of high-energy electrons has been proposed. Generally, the generation and propagation of runaway electrons are accompanied by the generation of X-ray. Therefore, the properties of X-ray can indirectly reveal the characteristics of high-energy runaway electrons in nanosecond-pulse discharges. In this paper, in order to explore the characteristics of runaway electrons and the mechanism of nanosecond-pulse discharge, the temporal properties of X-ray in nanosecond-pulse discharge are investigated. A nanosecond power supply VPG-30-200 (with peak voltage 0200 kV, rising time 1.2-1.6 ns, and full width at half maximum 3-5 ns) is used to produce nanosecond-pulse discharge. The discharge is generated in a tube-to-plane electrode at atmospheric pressure. Effects of the inter-electrode gap, anode thickness and position on the characteristics of X-ray are investigated by measuring the temporal X-ray via a diamond photoconductive device. The experimental results show that X-ray in nanosecond-pulse discharge has a rising time of 1 ns, a pulse width of about 2 ns and a calculated energy of about 2.310-3 J. The detected X-ray energy decreases with the increase of inter-electrode gap, because the longer discharge gap reduces the electric field and the number of runaway electrons, weakening the bremsstrahlung at the anode. When the inter-electrode gap is 50 mm, the discharge mode is converted from a diffuse into a corona, resulting in a rapid decrease in X-ray energy. Furthermore, both X-ray energies measured behind the anode and on the side of discharge chamber decrease as anode thickness increases. The X-ray energy measured on the side of the discharge chamber is one order of magnitude higher than that measured behind the anode, which is because the anode foil absorbs some X-rays when they cross the foil. In addition, the X-ray energy behind the anode significantly decreases with the increase of the thickness of anode aluminum foil. It indicates that the X-ray in nanosecond-pulse discharge mainly comes from the bremsstrahlung caused by the collision between the high-energy runaway electrons and inner surface of the anode foil. Therefore, increasing the thickness of the anode foil will reduce the X-ray energy across the anode film.