= Alvarez hydrogen-bubble-chamber reconstruction and resonances
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<Luis Walter Alvarez>'s program extended the <Glaser bubble-chamber experiment> into large <hydrogen bubble chambers> and systematic analysis. His lecture credits <John G. Wood>, an accelerator technician, with early hydrogen tracks, and emphasizes technicians' responsibility for chamber development.<Recent Developments in Particle Physics by Luis Walter Alvarez>[Recent Developments in Particle Physics, lecture 11 December 1968; institutional report UCRL-18696, printed pp. 12–16, Fig. 2]{ref}
Alvarez's 1956 report describes a ten-inch <hydrogen bubble chamber> in a steady <magnetic field>, exposed to a $700\,\mathrm{MeV}$ negative-<pion> beam for <proton> scattering. <Liquid> <hydrogen> was the target. Horizontal windows admitted illumination and stereo viewing; a shielded light source let bubble-scattered <light> reach the lenses. A <temperature gradient> initially restricted sensitivity near the top. Tilting and fast recompression improved uniformity.<Liquid Hydrogen Bubble Chambers by Luis Walter Alvarez>[Liquid Hydrogen Bubble Chambers, UCRL-3367, 4 April 1956, PDF pp. 5–7: ten-inch chamber, optics, recompression and scattering exposure]{ref}
The same report compares tracks without a <magnetic field> against straightness expectations, testing spurious curvature. <Multiple Coulomb scattering> remained a limitation. This separates an instrumental check from the physical <momentum> inferred with the field on.<Liquid Hydrogen Bubble Chambers by Luis Walter Alvarez>[UCRL-3367, PDF p. 7, paragraph beginning “The no field tracks”]{ref}
The scientific opportunity is to turn a visible geometry into a test of an invisible intermediate state. The <bubble-chamber pressure cycle> prepares the sensitive target; <bubble-chamber track readout> supplies geometric measurements. Neither step alone identifies a <particle resonance>.
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