High Speed Scan (HSS) velocimeter
Product description
IDIL’s PDV, referred to High-Speed Scan, is a fiber-optic, compact (19″ 5U rack), modular system consisting of a mainframe and removable measurement slots. Up to four slots can be used simultaneously and independently. The measurement slots can be configured for PDV, Triature PDV, or Triature fibered VISAR.
- PDV channel —Best speed resolution in the range of 0-20 km/s with our Photon Doppler Velocity (PDV) slots. PDV can measure both interfaces, projectiles and debris speeds.
- VISAR channel —Best temporal resolution in the range of 0-2 km/s with our Velocity Interferometer System for Any Reflector (VISAR) slots. VISAR is the only technology allowing accurate detection of elastic wave precursors.
HSS ARCHITECTURE
A heterodyne velocimetry system, known as PDV (VH in French), is an optical instrument that uses the Doppler effect to determine the velocity of a target moving at high speed over a very short period of time. The Doppler effect is the frequency shift df (i.e. wavelength shift) of an electromagnetic wave reflected by a moving object – its value is directly proportional to the velocity of that object.
The optical interferometer allows two light waves to interfere/beat with each other, one being reflected by the target and the other being a reference wave. The result is an analog signal whose frequency spectrum, obtained by Fast Fourier Transform (FFT), directly shows the Doppler shift from which the evolution of the object’s speed over time is calculated using a sliding window.
When the reference wave comes directly from the main laser, it is called a homodyne interferometer; when a second laser is used for the reference, it is called a heterodyne interferometer. Although more complex in its implementation, the latter configuration allows extending the speed range up to 20 km/s and determines the direction of the object’s movement. The homodyne setup can be preferably used for low-speed regimes.
SPECIFICATION
| *Depending on the width of the analysis Fourier window | |
| High Speed Scan | |
| Velocity range | 1m/s to 20 km/s |
| Offset Frequency Tunability range | -3 to +15 GHz |
| Measurement uncertainty* | Δt Δv = 150 ns.m/s (i.e. +/- 3 m/s for 50 ns window width) |
| Temporal uncertainty (after Fourier Transform processing) | 5 ns |
| Dynamics | >27 dB (limited by scope performance) |
| Minimum object reflectivity | -60 dB |
| Maximum number of channels | 4 |
| Maximum optical power | 400 mW (each channel) |
| Optical power stability | 1% over 8 hours |
| Optical frequency stability | 250 MHz |
| Optical connectors | E2000/APC |
| RF connectors | SMA |
| Control | Local or remote (Ethernet) |
| Trigger mode | Continuous or pulsed < 100 Hz |
| Height | 5U (465 mm) |
FEATURES
IDIL’s PDV, referred to High-Speed Scan, is a fiber-optic, compact (19″ 5U rack), modular system consisting of a mainframe and removable measurement slots. Up to four slots can be used simultaneously and independently. The measurement slots can be configured for PDV, Triature PDV, or Triature fibered VISAR; with the major and unique feature of allowing two slots to be coupled together (a single probe for two types of measurements).
The High-Speed Scan system features a touchscreen that allows the user to easily configure the instrument through a simple and intuitive graphical user interface (“GUI”). Additionally, the user can communicate remotely via a dedicated protocol.
The use of optical fibers enables the instrument to be positioned far from the measurement point, with distances of up to several hundred meters.
Each slot includes a red laser that can be activated from the GUI, allowing the user to easily visualize the target point of the optical probe without disconnecting the fiber patchcords.
Each slot provides adjustable optical power up to 400mW (guaranteed 350mW), enabling measurements in challenging conditions (long distance to the object, low object reflectivity, or object tilt).
Each PDV slot integrates ultra-low-noise photodetectors with very high dynamic range and bandwidth, allowing measurement of speeds up to 20 km/s.
Each PDV slot features an auxiliary optical input to capture the signal reflected by the target using another probe. This “dual-fiber” also called “bi-fiber” mode can be activated via the GUI.
Each PDV slot includes a variable optical attenuator controlled through the graphical interface, enabling easy adjustment of the beat signal amplitude without the risk of saturating or damaging the photodetector or digitizer input.
The reference laser is tunable in wavelength, allowing fine control of the frequency offset between the reference wave (carrier frequency) and the main wave. This offset can be defined advantageously between -3GHz and +15GHz, depending on the velocity range, direction of movement, and digitizer performances.
Both the main and reference lasers are ultra-stabilized, ensuring high signal-to-noise ratios and excellent velocity measurement accuracy.
The system can be switched via the GUI to homodyne interferometer mode with a fixed offset of 80MHz for low-speed measurements.
Target illumination can operate continuously or in pulsed mode triggered by an external signal to prevent potential heating of the target.
The included CAFEINE™ software allows easy signal analysis. Developed by CEA, it is specifically designed for high-velocity resolved measurements and the analysis of multiple frequencies (e.g., in spray scenarios).
An activation key is required for software installation, with one named license per workstation (unlimited number of licenses). (OS: Windows 10 and beyond).
A flight-case-style transport box is provided with the HSS system to facilitate transport and operation in experimental areas.
- Shock physics
- Material studies
- High explosives
- Gas gun
- Particle stallation
- Detonics
- Plasma
- High energy-density physics (HEDP)
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