Analytical Technologies Singapore

streak camera

Detonation Analysis by using the Solid-State-Streak-Camera S3C-1

Visualisation of Detonation Front Curvature with Nanosecond Temporal Resolution

The chemical reaction inside a homogeneous explosive agent can be initiated at a small spot and will then propagate spherically from this spot. The propagation can be observed as optical emission at the interface between the explosive and the air. Measurement along only one line is sufficient, but must be recorded with high temporal resolution in the nanosecond range to capture fast reactions. The spherical propagation leads to the curvature of the detonation front. The emission is expected to start in the center of the line and then propagate symmetrically along the line toward the edges. The analysis of this curvature allows the determination of the dynamic processes inside the explosive.

Instead of using a conventional tube-based streak camera, the solid state streak camera S3C-1 is used. The propagation of the optical emission is completed within 2 µs and the S3C-1 allows to capture this with 10 ns temporal resolution. A post trigger feature of the S3C-1 is used to capture the emission without being affected by the strong jitter of the detonator. An application note describes the setup and experimental details. It is available on request.

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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

 

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