PKE Nefedov*

Hardware Description

Schematic view into the PKE-Nefedov Experimental Block

Fig.1: The PKE-Nefedov hardware onboard the ISS consists of two components: the Experimental Block and the so-called Telescience Module. The Experimental Block is shown in the figure. It can be divided into three different parts:
Part I: Experimental setup. Includes the rf plasma chamber (3, see also Fig.2), a symmetrical parallel plate reactor filled with argon with assembled microparticle dispensers (2 = dispenser drive), rf-generator (7), pressure control system (9), cameras (4), and lasers (8) mounted on a translation stage. The rf generator is a special development for lowest rf power values, which are required for stable and large complex plasma systems and for plasma crystal formation. Two CCD-cameras provide two different magnifications of the complex plasmas. The overview camera shows about a quarter of the field between the electrodes, 28.16 x 21.45 mm2, while the high resolution camera is used for detailed views inside the overview field covering 8.53 x 6.50 mm2. On top of the Experimental Block a vacuum connection (6) is used to pump the experimental setup. This vacuum port is contacted to outer space.
Part II: Electronics (5, 10) for part I and the system electronics (PC, video and main power control).
Part III: Experiment computer. Allows real time control of the plasma. Electrical signals produced by the experiment computer and the two video signals are contacted out of the container (1) and are controlled by the Telescience Module (see Fig.4). The computer visualizes the experimental data and can be used to control the experiment manually. Time codes (VITC signals) are inserted into the video frames and stored on two High-8 video recorders. The original video tapes are transferred to ground by the cosmonauts. The Telescience Module has the capability to transfer experimental data and video to ground and receive commands from ground, allowing full telescience control of the experiment by the scientists.
Schematic view of PKE-Nefedov

See also the PKE-Nefedov ''Promotion Video'' (4:30, 45 MB)...

Monodisperse particles of different sizes – 3.4 µm and 6.8 µm in diameter, as well as a mixture of both sizes – can be injected into the plasma chamber, between the two electrodes. The microparticles are illuminated by a thin (~150 µm) sheet of laser light perpendicular to the electrode system (produced by a laser diode and cylindrical optics). For each particle size one laser is installed, which is adjusted in power and optics to achieve best results. The reflected light from the microparticles is observed with two monochromatic video CCD-cameras (768 x 576 pixels, 25 Hz, 8-Bit) with different resolution. The microparticles can be identified in a single video frame and are then followed in time to investigate their dynamical behaviour. The frame rate is 25 Hz, which is faster than the complex plasma frequency of ~10 Hz. Slow speed scanning of the laser and optics into the depth of the plasma chamber is used to measure the 3D positions of the microparticles.

Scheme of the PKE-Nefedov Plasma Chamber

Fig.2: Cross section through the heart of the PKE-Nefedov experiment: the plasma chamber ((3) in Fig.1). This is a square vacuum chamber with a size of 10 x 10 cm2 made of glass. The rf electrodes are flat circular plates, made from stainless steel, with a diameter of 4.2 cm, where a dust dispenser is integrated in the center of each side. The microparticles are injected into the discharge region between the electrodes by an oscillating up and down motion of the dispensers. The particles are accelerated inside the reservoir and released through a sieve with a meshsize slightly larger than the particle diameter. The electrode distance is 3 cm. The excentric field of view of the CCD cameras is shown here in green.
plasma chamber

The Actual Experiment Hardware

Fig.3: Here we see the PKE-Nefedov experiment hardware before integration into its sealed cylindrical containment. On the left side there is the CCD camera electronics connected to both CCD cameras that are looking into the plasma chamber (center). On the right side there is the gas supply system (with the argon gas bottle) that is connected on the ground to a vacuum pump. On the ISS the experiment is connected directly to open space. (Unfortunaletly, the vacuum port onboard the ISS is a rather narrow line which made it necessary to upgrade PKE-Nefedov with a turbo-molecular pump at the vacuum port. This pump was installed in Sept. 2001.)
The hardware was built by MPE and externalKayser-Threde.

PKE-Nefedov and the Telescience Unit

Fig.4: PKE-Nefedov and its control and data acquisition system, the Telescience Unit. The naming is due to the fact that the experiment can totally be run from this unit which can be at any remote place. The original plan was to operate PKE-Nefedov in orbit from the Telescience Unit on the ground via a satellite link, but unfortunately the satellite failed so that only a telemetry mode could by established. The Telescience Unit was also carried into orbit and the data tapes were then taken to earth by the returning ISS crew.
Telescience Unit

See pictures of PKE-Nefedov onboard the ISS...

Pic of Anatoli

*In Memoriam
Anatoli P. Nefedov

On February 19, 2001 our russian friend, colleague and leading project scientist of the Plasmakristall-Experiment (PKE) passed away. In memory of his outstanding contribution to the field of complex plasmas and to PKE the project will be named after him - PKE-Nefedov.

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Updated: 01/2006 Michael Kretschmer