G. Harigel

Pulse stretching in a Q-switched ruby laser for bubble chamber holography.

In testing a holgraphic particle track recording system for the Fermilab 15-ft bubble chamber, it was shown that the peak power of Q-switched laser pulses (~50-ns duration) at the required energy gave rise to boiling during the chamber expansion. A pulse stretching technique is described which was developed to reduce the peak power. Applied to a ruby laser (oscillator and three amplifiers) with a maximum Q-switched output of 30 J, pulses of up to 100-μs duration with coherence up to and exceeding 11 m at 2.5 μs were produced. These pulses were amplified to ~5 J without shape degradation. The considerably increased coherence length will find applications in many fields of pulsed holography, and its use with fiber optics is particularity promising.

Inclusive neutral kaon production in 70 GeV/c K+p interactions

Abstract The inclusive production of neutral kaons in 70 GeV/ c K + p interactions is studied with the CERN BEBC bubble chamber. The (semi-)inclusive cross sections are interpreted in terms of the various strangeness channels leading to neutral kaon production. The invariant inclusive cross section for kaon production is studied as a function of p t 2 and the Feynman variable x . The latter distributions are considered both “raw” and corrected for the presence of K 0 s resulting from K ∗ decay. They are compared with the predictions expected from the Regge-Mueller formalism, the recombination model and fragmentation models.

Charged pion production in 70 GeV/cK+p interactions

Inclusive charged pion production is studied in an exposure of BEBC, filled with hydrogen, to an incidentK+ beam of 70 GeV/c. Total cross sections for pion production and inclusive longitudinal and transverse momentum distributions of π−s and of positive particles are presented and compared with data at lower energies. Earlier evidence for scaling in the fragmentation regions is confirmed. The central region π− cross section increases proportionally topLAB−1/4; positive particles show almost no energy dependence atx=0. Particle ratios π+/π− are studied as a function ofx andy* and a comparison with 70 GeV/cK−p data is made. Analysis of structure functions for (ππ) pairs and of particle production associated with π± triggers at large |x| in the context of quark/parton models, provides qualitative evidence for the diquark-quark structure of the proton.

On the formation of narrow bubble tracks by a laser beam in argon, nitrogen and hydrogen bubble chambers

Long bubble tracks, <1 mm in diameter, have been produced in liquid argon and nitrogen with a nitrogen laser beam (h = 337 nm), offering subnanosecond pulses with small beam divergence. Bubble formation was observed over a wide range of operating conditions, including those for ordinary bubble chamber operation, with a laser pulse of 10 #J. Typical bubble densities obtained were 4-8 bubbles/cm, with maximum densities of 20 bubbles/cm. In liquid hydrogen, tracks of 3 m visible length were observed with track diameters from 1.5 to 6 mm and bubble densities from 2 to 25 bubbles/cm. Results and applications will be discussed.

Holographic recording of cosmic ray tracks in BEBC

We report on a successful test of holography in the Big European Bubble Chamber (BEBC) at CERN, which was filled with a heavy neon—hydrogen mixture. During the test of a modified in-line scheme we photographed bubble tracks longer than 1 m, which were produced by cosmic rays. The smallest bubbles, which were recorded with excellent contrast, had a diameter of ≳ 120 μm. This presents an improved resolution of a factor of five compared to photos taken with conventional cameras.

Laser pulse stretching via enhanced closed loop control with slow Q-switching

Abstract A pulse stretching technique in a Q-switched ruby laser oscillator is described. The major improvement to our previously developed pulse stretching circuit consists in a more adequate waveform for the feedforward part. This new system gives fairly flat pulses with adjustable duration up to ∼ 100 μs and good coherence length in excess of 11 m. The cavity is followed by several amplifiers and produces light energies up to 8 J for holographic recording of particle tracks in the Fermilab 15-foot bubble chamber. The considerably increased coherence length will find applications in many fields of pulsed holography and its use with fiber optics is particularily promising.

Cross sections and multiplicity distributions forK+p interactions at 70 GeV/c

Cross sections and charged multiplicity distributions forK+p interactions at 70 GeV/c are presented and compared withK+p data at other energies. Comparisons are also made with available π+p,pp, andK−p data.

Scintillation light from liquid argon and its use in a new hybrid detector

Abstract Scintillation light, produced by 200 MeV/ c pions in a liquid argon bubble chamber/calorimeter was measured. Results from the test device show that this signal could be used in future large bubble chambers to trigger the flash on the occurrence of an interesting event. Furthermore, this signal give rough information about total track lengths, hence energy contained in massive electromagnetic and hadronic showers, and could complement measurements obtained by charge collection.

A giant argon bubble chamber with long sensitive time for nucleon decay experiments

Abstract A giant argon bubble chamber could be a suitable detector to investigate the decay modes of nucleons in an unbiased way. We are investigating the possibility of operating such a chamber with a track sensitive duty cycle of up to ∼ 50%. A small and not very clean bubble chamber has been successfully operated in an expanded pressure stabilized mode with a duty cycle of 10%. A tentative design of a 3000 m 3 argon bubble chamber is discussed.

Simultaneous operation of a liquid argon detector as bubble chamber and calorimeter

Abstract The first successful operation of a new detector, filled with liquid argon is described. It can be used simultaneously as bubble chamber and calorimeter, and may find interesting applications at high-energy accelerators.