A new measurement of the elastic scattering of 250-GeV/e negative pions by electrons provides form-factor results from 0.0368&q~& 0.0940 (Gev/c)2. These measurements determine the mean square pion radius to be (r~~) = 0.439 + 0.030 fm' or (r~~) 'I~= 0.663 + 0.023 fm. Comparisons are made with previous elastic-scattering experiments as well as with results obtained from electroproduction experiments, e e annihilation experiments, and phenomenological analyses.

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A method for containerless liquid-phase processing was developed which has practical application in process and property research on virtually any material which is involatile at the melting point. It combines aerodynamic and acoustic forces to support and position the levitated material. The design provides forced convection control of the thermal boundary in the gas surrounding beam-heated specimens, which stabilizes the acoustic forces and allows acoustic positioning necessary to stabilize the aerodynamic levitation forces on molten materials. Beam heating and melting at very high temperatures was achieved. Experiments were conducted on specimens with diameters in the range 0.25–0.4 cm, of density up to 9 g/cm3, at temperatures up to 2700 K, and in oxygen, air, or argon atmospheres. Unique liquid-phase processing results included deep undercooling of aluminum oxide, glass formation at exceptionally small cooling rates, complete melting and undercooling of YBa2Cu3Ox superconductor materials, direct formation of the YBa2Cu3Ox from the liquid phase, and the vaporization of volatile constituents from a low-liquefaction point glass to form a refractory, high melting material. The application of rapid containerless batch processing operations to materials synthesis is discussed.

A single-axis acoustic levitator was constructed and used to levitate liquid and solid drops of 1-3 mm in diameter at temperatures in the range -40 to +40 degrees C. The levitator comprised (i) two acoustic transducers mounted on a rigid vertical support that was bolted to an optical breadboard, (ii) an acoustic power supply that controlled acoustic intensity, relative phase of the drive to the transducers, and could modulate the acoustic forces at frequencies up to 1 kHz, (iii) a video camera, and (iv) a system for providing a stream of controlled temperature gas flow over the sample. The acoustic transducers were operated at their resonant frequency of approximately 22 kHz and could produce sound pressure levels of up to 160 dB. The force applied by the acoustic field could be modulated to excite oscillations in the sample. Sample temperature was controlled using a modified Cryostream Plus and measured using thermocouples and an infrared thermal imager. The levitator was installed at x-ray beamline 11 ID-C at the Advanced Photon Source and used to investigate the structure of supercooled liquids.

We have performed an experiment in a 100-GeV/c negatively charged-pion beam at the Fermi National Accelerator Laboratory to measure the form factor of the pion by elastically scattering pions from the atomic electrons in a liquidhydrogen target. The square of the pion form factor as a function of the square of the four-momentum transfer, q 2 , is defined to be the tr-e elastic (el) differential scattering cross section after radiation correction, divided by that predicted for a point (pt) pion;(da/dqX^ida/drtplFrtf)?In the second line the point-pion cross section is written in terms of the fine-structure constant ot and F w (q 2 ) has been expanded in powers of q 2 . In our experiment the maximum recoil energy of the electron was 84 GeV corresponding to q max 2 = 0.086 (GeV/c) 2 .In this Letter we present data University Report No. OITS-73, 1977 (unpublished). 7 Glennys R. Farrar and Darrel R. Jackson, Phys. Rev. Lett. 35, 1416Lett. 35, (1975.on the pion form factor in the range 0.03 ^ q 2 <0.07 (GeV/c) 2 . 3The charged pion is a particularly simple sysr-tern compared to the proton. Its isovector character implies that it couples almost exclusively to the p meson. In the timelike domain the pion o-form factor has been well measured experimentally. 1 Measurements of the pion form factor at i spacelike momentum transfers, coupled with analyticity, provide a useful test of the vectordominance model. Furthermore, the size of the pion can be extracted directly from these spacelike measurements. I 2The first direct measurement 2 of the pion form 0 • factor by n-e elastic scattering obtained (r n 2 ) = 0 o 61±0.15 F 2 . Our experiment provides an imis proved measurement through refinement of the 01 techniques employed in the earlier experiment [n and by exploiting the higher-momentum-transfer "he values available at Fermilab. The apparatus is shown in Fig. 1. The princii pal features of the experiment are as follows:We have measured the electromagnetic form factor of the charged pion by direct scattering of 100-GeV/c 7r" from stationary electrons in a liquid-hydrogen target at Fermilab. The deviations from the pointlike pion-scattering cross section may be characterized by a root-mean-square charge radius for the pion of (r^2) 1^2 = 0 e 56± 0,04 F.