Analytical Technologies Singapore

Framing Camera

Supersonic Electrical Discharge in Water

Researchers at Loughborough University have been using a SIMX framing camera at frame rates up to 100 million frames / second to capture the initial stages of supersonic electrical discharges driven by nanosecond rise time, high-voltage ( 100 kV) impulses applied across a pair of electrodes mounted in water.

This research in high voltage breakdown in water, has progressed our understanding of how high-power ultrasound waves generated in a liquid by a high-voltage pulsed source can be used for industrial applications such as rock fracturing or in the medical or food industry domains to kill bacteria in a sterilisation process. The SIM camera was contained within a Faraday cage and viewed the electrodes mounted in a water tank. Pressure variation with different voltage rise times and interelectrode gaps were measured using a set of hydrophones placed 0.5m from the source.

This sequence shows results for an electrode gap of 3 mm and voltage rise time of 30 ns which corresponded to a streamer propagation speed of 63 Km/s and a peak pressure of 0.25 MPa.

Consistent peak pressures between 0.1 MPa and 1.1 MPa were found for inter-electrode gaps between 1 mm and 12 mm. The research concluded that the inter-electrode gap had a significantly greater effect on peak pressure than rise time for the same input energy.

The SIM camera’s nanosecond timing accuracy provided the flexible delays and exposure times required to capture and freeze the motion of these extremely fast events. To accommodate the different illumination conditions required to see both the source electrodes and the event, the camera control software “image merge” feature was used to overlay a static sequence, which used longer exposure times, with the dynamic sequence which used much shorter exposure times.

These merged images provide context and the relative positions of the event and electrode for all the tests.

Congratulations to Jessica Stobbs for receiving the EAPPC (Euro-Asian Pulsed Power Conference, Seoul, S. Korea, 2022) outstanding Young Researcher Award with this research.

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Advancing forensic interpretation of ballistic wounds

Ultra high-speed photography has been used by scientists at the Massachusetts Institute of Technology to study high-velocity micro-particle impact on gelatine and synthetic hydrogel. Potential advancements are, guiding the design of drug delivery methods using accelerated microparticles and the assessment of explosive–related injuries for better forensic interpretation in cases where fragments originating from explosions can cause severe tissue damage injuries. Micro debris, which typically travels at supersonic velocities, can cause serious injury by penetrating deep into tissue where it is hard to detect using standard medical imaging methods.

Multi–frame sequence showing a high-velocity impact on 10 wt% gelatine at 1290 m/s.

The research investigates the high-velocity impact response of gelatine and synthetic hydrogel samples using a laser-induced microparticle impact test platform for launching and imaging supersonic micro-particles travelling up to 1,500m/s. The micro-particles, typically less than 10um in diameter are captured prior and during impact penetration into translucent gels using a Specialised Imaging SIMX16 ultra high-speed multi-frame camera, capable of recording up to 16 images with nanosecond interframe time and short exposure times (down to 3ns) to stop motion blur. Illumination was provided by the Cavilux 640nm wavelength laser.

The impact response was quantified using the images by measuring pre-impact velocity, particle penetration depth and charted against time. These results were compared against a Poncelet predictive model for different gelatine samples. Further tests and measurements were conducted using an engineered protein hydrogel to investigate whether the Poncelet model could be applied to other soft materials which might be expensive to manufacture or otherwise in short supply.

The results indicate the Poncelet model provided a reasonable prediction of micro particle penetration and could offer an initial estimation of deformation of soft materials at high strain rates in more complex models.

See the Research Article here >> https://www.specialised-imaging.com/application/fi…

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Triggering for microsecond accuracy

Accurate triggering of framing cameras to capture fast events is one of the crucial aspects of high-speed imaging. Adding more instrumentation such as streak cameras and flash illumination can lead to a complex array of instrumentation, particularly when it comes to synchronising all aspects of data capture for one single microsecond timescale event.

Specialised Imaging’s SIM framing cameras can greatly simplify this trigger synchronisation process, with a built-in timing generator and control software to set up trigger outputs to these external devices.

If a streak camera is used to capture the same event it can be connected to the SIM’s (optical) auxiliary port and connected to the SIM’s trigger output to allow the streak camera trigger delay adjustment via the SIM camera control software. Any flash illumination can be connected to the SIM’s dedicated flash trigger (output) connection for timing adjustment also using the camera control software.

This application note describes how a SIM camera was used to capture energetic events, where microsecond accuracy was required. The SIM camera was used to trigger synchronise a streak camera and flash unit to capture images for detonator case expansion and tip velocity measurement.

Read the application note

Camera: SIMX-8 Resolution: 1280×960 px Exposure time: 100nS Interframe time: 4.27uS Frame Rate: 234K FPS Event: Detonator Illumination: Back illumination – AD500mage: New and old SIM (8 channel) camera design

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SIM Cameras now optimised for Ultra High-Speed Multispectral Imaging

Specialised Imaging’s latest version of the SIM ultra high-speed framing camera is making multispectral imaging simpler with the option of user interchangeable filters.

Specialised Imaging is continually evolving its products to meet new and challenging requirements. In response to increased requests, the latest evolution in the SIM cameras makes it simple to interchange standard size filters for multispectral imaging – capturing different wavelengths on each channel. Multispectral imaging was possible on previous SIM models, but the new SIM design simplifies the user exchange of filters for all channels.

This evolutionary step in the SIM camera design was driven by requests in the field of energetic materials research. Using filters in a camera allows researchers to obtain spectral, spatial and temporal information for comparing different energetic materials by focussing on the different spectral signatures. The nature of energetic materials mean you need an ultra-fast, light sensitive camera that can respond to a broad range of wavelength to provide a flexible solution for this and other applications.

Users can now easily interchange filters on all eight channels. The SIMX camera captures one high resolution image per channel, offering the potential to capture 8 mono/filtered images and potentially two monochrome and two full colour images using red, green & blue filters. Similarly, the SIMD camera captures two images on each of its eight channels, offering the capacity to capture 16 mono/filtered images, or four mono and four full colour images. By responding to our customer input and requests, this capability expansion of the SIM cameras continues to support new and novel applications for the advancement of research.

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Streak / Framing Camera Provides Unique Insight into Nano Events

Researchers on several projects have successfully used Specialised Imaging Simultaneous Multichannel Framing Camera and Streak Camera Systems to provide unique insights into an ultra-fast events.

Specialised Imaging ultra-fast camera systems offer scientists involved in electrical discharge, biomedical and energetic events research the potential to simultaneously record framing images and streak images.

Ultra-fast imaging and simultaneous streak image capture offers a unique insight into transient events that cannot be achieved with single-point measurements. Ultra-fast framing images show extremely detailed two-dimensional spatial information about the event, whereas the streak image is a continuous one-dimensional record with picosecond temporal resolution. When combined these images provide a unique visualisation of transient nanosecond timescale events.

Specialised Imaging’s system enables researchers to couple a streak camera directly into the same optical path used in their SIM ultra-fast framing cameras. This innovation allows for the capture of framing and streak data on the same event using the same optical path for direct correlation of 2D and streak image data. The combination streak and framing camera has allowed researchers to attain higher performance levels using dual camera systems with different optical inputs. Benefiting from using a common optical input and dedicated output window, the Specialised Imaging Simultaneous Multichannel Framing Camera and Streak Camera system drastically simplifies optical set up and eliminates perspective distortion (parallax errors). Beneficially, the set-up also allows use of an existing streak camera which can still be used independently.

Capable of capturing data at 1 billion frames per second, the SIM range of ultra-fast framing cameras offer the ultimate in ultra-high-speed imaging performance to scientists and engineers across all disciplines. The proprietary optical design of SIM cameras offers up to 32 images without compromising shading, or parallax. High resolution intensified CCD sensors controlled by state-of-the-art electronics provide almost infinite control over gain and exposure to allow researchers the flexibility to capture even the most difficult phenomena. In addition to enabling simultaneous streak and framing experiments, the optical port on the SIM camera can be used to couple high-speed video cameras for longer record durations, or to integrate a mass spectrometer for hyperspectral

Case Study

Researchers at the University of Michigan used a Specialised Imaging Simultaneous Multichannel Framing Camera and Streak Camera System to capture images of bursting microscopic droplets releasing the fluid within by focused ultrasound, and ultimately understand how this process can safely and effectively be applied to the delivery of drugs within the body.

Read the case study

Application Note

Ultra-high Speed Framing and Streak Camera Imaging of C4 Explosive

The University of Rhode Island used a Specialised Imaging Simultaneous Multichannel Framing Camera and Streak Camera System in research to quantify the shock speed and qualify the axisymmetric detonation development of a C4 booster test piece.

Read the Application Note

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Revolutionising Drug Delivery within the Body

Research at the University of Michigan used a Specialised Imaging SIMD16 ultra high speed multi-channel framing camera to capture images of bursting microscopic droplets releasing the fluid within by focused ultrasound, and ultimately understand how this process can safely and effectively be applied to the delivery of drugs within the body.

Imagine medical ultrasound propagating waves through the body at approximately one million cycles per second. Within the body, the waves encounter carrier droplets filled with a drug or therapeutic payload. The acoustic pulse of the ultrasound expands and contracts these carrier droplets until they burst and release their contents, delivering them at exactly the right place and at exactly the right time, without damaging any surrounding living tissues, structures, or fluids. Pursuit of a safe and precise way of applying acoustic droplet vaporisation (ADV) to burst perfluorocarbon (PFC) ‘shell’ carrier droplets was one aim of Prof. Oliver Kripfgans and his colleagues, including Prof. Mario Fabiilli, at the University of Michigan.

Capturing a tiny moving droplet

One of the main challenges the researchers faced was the micrometre length scale of the droplets they wanted to observe. To see the droplets with enough detail required zooming into a 20 m x 20 m area to view a single droplet just two or three microns in diameter to observe it burst. The set up mounted the camera on a large optical “bread board” that was supported vertically above a standard laboratory microscope. A flow tube containing fluid was placed below the microscope objective.

To find a droplet, the field of view was initially large (1 mm x 1 mm) using 10x magnification. Once a droplet was found, its position was centred in the field of view using a fine adjustment pump before increasing the magnification to 100x.

The ultrasound beam was aligned with the camera field of view to ensure correct and repeatable ultrasound application on the droplet.

Why use a SIMD16?

The SIMD16 camera offered Prof. Oliver Kripfgans’ team sixteen full frame images (1360 x 1024 pixel resolutions), at frame rates of up to 200Mfps. Ultimately, the team chose the SIM because of its ability to capture clear images of both short and long term behaviour of an event by independently configuring each image channel – delay from trigger, exposure time, intensifier gain etc. and the unique feature of acquiring simultaneous streak camera image data using the same optical path.

Lighting the experiment

The second challenge of the experiment was achieving sufficient lighting. The use of a microscope to achieve the micrometre scale observation window had the inherent negative effect on the amount of light transmitted to the camera. To overcome this, the team used an SI-IF300 (300 Joule, 12 s) flash system with fibre optic output, which provided enough light for the duration of all the events to be captured.

Specialised Imaging’s equipment made capturing the necessary images possible, the sensitivity of camera and power of light compensated for the inefficiency of the microscope. – Prof. Oliver Kripfgans

The resulting images include frames before, during and after the ultrasound arrival. Although the number of images captured was 16, this was sufficient to observe the expansion and contraction of the internal fluid prior to the droplet shell bursting as shown below.

To assist with capturing more data between consecutive (or alternate) images, an Optronis SC10 streak camera, sharing the same optical path as the framing camera, was used to identify events and refine exposure delays of the framing camera. Images from the streak camera provide continuous 1-dimensional image data across the centre of the framing camera field of view (either left to right or top to bottom) with 15.6 ns between lines.

The example below is an early streak image captured with a top to bottom streak “slit”. This clearly shows the number of oscillations before the eventual bursting of a droplet.

Repetition enabled the team to establish how many acoustic cycles are required to explode the droplets, see the different patterns created and understand how droplets affect each other, and other objects in the immediate area.

Establishing the performance of ADV

In the research at the University of Michigan, ultra high speed imaging established that the ultrasound frequency and type of perfluorocarbon influenced the number of ultrasound cycles required to burst a perfluorocarbon droplet, and that the ADV did not damage surrounding tissue. Typically, around 13 cycles of ultrasound induced oscillation caused the perfluorocarbon droplet burst.

ADV for improved drug administration

Research performed by Prof. Fabiilli evidenced that ADV offers an unparalleled advantage in drug administration, with the ability to precisely control where and when drugs, or other therapeutic agents can be delivered within a body. This method is far more targeted with less collateral damage than more traditional methods of drug delivery, which flood the patient’s system with much higher drug doses to achieve the same effect, but cause problems elsewhere in the body. Example applications for ADV could include intravenous therapy for prostrate or breast cancer, where droplets injected into the blood stream would be activated at the relevant site. In the regrowth of blood vessels after ischemic damage, droplets containing promoters for vascular growth could be introduced during surgery on a scaffold implant then activated in situ by ADV at intervals to assist recovery.

Research established that ADV can be used to release more than one drug, monitoring drug A, and then releasing drug B when appropriate. Ultra high speed imaging has enabled an understanding of the interaction between two carriers. Without the SIMD16 and streak cameras, a whole dimension of information would be missing from this understanding.

Working with our clients to help them achieve their objectives

In 2007-8 when the University of Michigan purchased the SIMD16, it was the only camera capable of capturing 16 images with the ability to integrate an external streak camera without sacrificing a channel (2 images) to provide simultaneous full frame and streak data. The solution proposed by Specialised Imaging’s SIMD16 and IF300 flash lamps was unique in terms of delivering the required setup flexibility with a suitable lighting source. Specialised Imaging was very much the tool maker and Prof. Kripfgans the machinist. We delivered the tools he needed to orchestrate his experiment.

Specialised Imaging is user orientated and flexible by desire, always aiming to deliver the highest quality and to meet, and hopefully exceed, client expectations in terms of both product performance and service. In the case of the SIMD16, which was very new at the time of the University of Michigan research, we were able to respond quickly to feedback from Oliver. For example, we modified the software so that the camera could be triggered manually while in focus mode at the precise instant when the micro droplet was in the correct field of view. We try to be as available as possible, appreciating that the users of our cameras and equipment do not necessarily keep to regular working hours!

Frank Kosel, President, Specialised Imaging Inc.

Where is the University of Michigan’s SIMD16 after over a decade of use?

 

Profs. Kripfgans and Fabiilli, and their group, continue to use the SIMD16 on a weekly basis, for the originally envisaged research of medical drug delivery using ultrasound techniques. Prof. Kripfgans was very enthusiastic to explain to us the research aims, methods employed and results using this unique combination of SIM framing camera and Streak camera instrumentation, and we thank him for his valuable time.

Resources:

Initial Growth and Coalescence of Acoustically Vaporized Perfluorocarbon Microdroplets

 

Revolutionising Drug Delivery within the Body Read More »