Other experimental devices available at BaPSF

ETPD

The Enormous Toroidal Plasma Device (ETPD) The ETPD device is housed on the main floor of the STRB building. The device was originally constructed as a tokamak and if run in that mode, it would still be the physically-largest tokamak in the world. The vacuum system interior dimensions are 2 m wide and 5 m high. The chamber is made from 1inch-thick stainless steel. The 32 toroidal magnets are made of Al slabs separated by glass insulators. Magnets plus chamber weigh in at 300 tons. The device is shown in Fig. 1. The long-term vision of BaPSF is to convert this chamber into a 24/7 operating basic plasma device with diagnostic capabilities equal to the LAPD. To attain that level of performance a separate infrastructure grant will be pursued in the future with various funding agencies. Figure 2 is a photograph of the ETPD plasma together with profiles, across the plasma column, of measured plasma parameters. The ETPD and its immediate diagnostics occupy 5760 sqft. of high-bay space. This area has a 25 foot ceiling and a 10 ton crane. There is an additional 2880 sqft. of low bay space for power supplies to service the ETPD. There is 1.3 MW available raw power fed by 12 kV lines and an additional 3 MW of 480/220 power in "rails" lining the walls surrounding ETPD to which circuit breakers may be attached. The STRB also has 2048 sqft. of machine shop space to service the building. The machines available include end mills and lathes (both manual and computer-controlled); band-saws; several welders; and cut-off saws. Presently the plasma source has a 20 cm diameter LaB6 cathode and plans are underway to upgrade this to a 60 cm source.

ETPD
Figure 1. Photograph of the ETPD device. The toroidal magnets are painted red and the vertical field coils are blue.

 

ETPD profiles
Figure 2: (left) Photograph of a helium plasma, using a vertical field to make the plasma spiral. Each ring is 30 m in circumference. The longest plasmas are 120 meters. (right) Plasma density and temperature measured with a Langmuir probe. The ion temperature, measured spectroscopically, equals Te. The central plasma beta is 1 at B0 = 150 G.

 


Small Plasma Device (SPD)

A small test device, shown in Fig. 3, was constructed using power supplies, a vacuum chamber and other hardware left over from the original 10 m-long LAPD device. Magnetic field coils were wound from water-cooled welding cable that limits the background magnetic field to 300 G. The plasma source is a 20 cm diameter LaB6 cathode which makes plasmas of density ne ∼ 1012cm−3 and the plasma is pulsed at 1 Hz. The machine is an excellent device for testing probes, small beams and experimental techniques before using them in the LAPD device. Users are welcome to utilize this machine for testing. Presently it is also being used to conduct a solar flare experiment that involves installation of internal field coils that are not possible to move in and out of the LAPD.

Test chamber (SMPD)
Figure 3: The SPD, four-meter test chamber. Probe drives for use in a solar flare experiment are on the right.

 


LAPTAG High School Plasma Laboratory

The BaPSF sponsors a high school outreach program known as the Los Angeles Physics Teachers Alliance Group (LAPTAG). High school students from the Los Angeles area use a small machine constructed especially for them out of spare parts from the facility. The LAPTAG device is shown in Fig. 4. Any high school or community college student is welcome to participate in this program. The students learn lab skills, build electronics and get lectures on plasma physics. The LAPTAG students have attended scientific meetings, including the APS-DPP annual meetings. LAPTAG meets every Saturday and nearly every day during in the summer.

LAPTAG high school plasma device
Figure 4: LAPTAG plasma physics device. An inductively coupled plasma source makes a pulsed (n_e ≤ 10^11/cm^3) plasma with a background field of up to 100 G. The plasma is 2 m long and 40 cm in diameter