Können Terroristen sich nukleare Massenvernichtungswaffen beschaffen? Dazu müssten sie ausreichende Mengen an waffenfähigem, spaltbarem Material stehlen. Selbst der Bau einer primitiven Atombombe erfordert einen hohen technischen Aufwand und Spezialisten. Wahrscheinlicher ist deshalb der Diebstahl einer kleinen taktischen Kernwaffe. Alternativ könnten Terroristen sich radioaktives Material aus zivilen Quellen beschaffen und daraus eine “Schmutzige Bombe” bauen. Eine solche radiologische Waffe wäre keine echte Massenvernichtungswaffe, doch ihre psychologische Wirkung könnte stark sein. Das macht sie für Terroristen attraktiv, weswegen diese Gefahr ernst genommen werden muss.

In 1952 D. Glaser demonstrated that a radioactive source's radiation could boil 135degreesC superheated-diethyl ether in a 3-mm theta glass vessel and recorded bubble track growth on high-speed film in a 2-cm(3) chamber. This Bubble Chamber (BC) promised improved particle track time and spatial resolution and cycling rate. Hildebrand and Nagle, U of Chicago, reported Liquid Hydrogen minimum ionizing particle boiling in August 1953. John Wood created the 3.7-cm theta Liquid Hydrogen BC at LBL in January 1954. By 1959 the Lawrence Berkley Laboratory (LBL) Alvarez group's "72-inch" BC had tracks in liquid hydrogen. Within 10 years bubble chamber volumes increased by a factor of a million and spread to every laboratory with a substantial high-energy physics program. The BC, particle accelerators and special separated particle beams created a new era of High Energy Physics (HEP) experimentation. The BC became the largest most complex cryogenic installation at the world's HEP laboratories for decades. The invention and worldwide development, deployment and characteristics of these cryogenic dynamic target/detectors and related hydrogen targets are described.

A method is developed for separating ν N interactions from interactions involving an intranuclear cascade in νNe scattering at a mean neutrino energy of 145 GeV. The fraction of events featuring a cascade is evaluated by using a sample of νNe charged-current interactions. It is found that the multiplicity of charged particles in the forward direction takes the same value for events with and without a cascade for 4< W 2 <550 GeV 2 . In the backward direction, cascade events have the charge multiplicity higher than the multiplicity for cascade-free events by 2.36 units. It is found that particles with momenta less than 2 GeV/ c make a dominant contribution to the rescattering process. A depletion of the fastest particles for W 2 <50 GeV 2 is observed, in accord with the formation-time concept.

Holography has been used successfully in combination with conventional optics for the first time in a large cryogenic bubble chamber, the 15-Foot Bubble Chamber at the Fermi National Accelerator Laboratory (FNAL), during a physics run in a high energy neutrino beam. The innovative system combined the reference beam with the object beam, irradiating a conical volume of approx1.5m3. Bubble tracks from neutrino interactions with a width of approx 120 micrometers have been recorded with good contrast. The ratio of intensities of the object light to the reference light striking the film is called the beam branching ratio (BBR). We obtained in our experiment an exceedingly small minimum- observable ration of BBR = (0.54 divided by 0.21) x 107. The technology has the potential for a wide range of applications. This paper describes the various difficulties in achieving the success. It required the development of laser pulse stretching via enhanced closed loop control with slow Q- switching, to overcome excessive heating of the cryogenic liquid by the powerful laser beam. A sophisticated system of light-absorbing baffles had to be installed to avoid stray light reaching the holographic film. Optical decoupling of classical and holographic illumination systems was required. Real and virtual image replay machines for holograms were built, tailored to our illumination technique.

Measurement of growing bubbles in a superheated liquid, having diameters in the 100μm range, were performed on photos taken in bright-field illumination with two different magnification optics and by an innovative holographic technique. The bubble tracks had been recorded during a neutrino experiment within a volume of ∼1.5m3 in the 15-foot bubble chamber at the Fermilab Tevatron. Three methods for the evaluation of the bubble sizes were applied for the classical photography. They are compared with each other and with measurements on holography replay devices.

Holography has been used successfully in combination with conventional optics for the first time in a large cryogenic bubble chamber. the 15-foot bubble chamber at Fermilab, during a physics run. The innovative system combined the reference beam with the object beam, irradiating a conical volume of similar to 1.4 m(3). Bubble tracks from neutrino interactions with a width of similar to 120 mu m have been recorded with good contrast. The ratio of intensities of the object light to the reference light striking the him is called the beam branching ratio. We obtained in our experiment an exceedingly small minimum-observable ratio of (0.54 +/- 0.21) x 10(-7). The technology has the potential for a wide range of applications. (C) 1999 Elsevier Science B.V. All rights reserved.

The development of holography for large cryogenic bubble chambers, which extended over almost one decade, is described. It culminated in the successful application of this ambitious technique to the 15-foot Bubble Chamber at Fermilab. During an exposure to the neutrino beam, produced by 800 GeV/c protons on the production target, over 110'000 good holograms were taken simultaneously with conventional photographs. Bubble tracks with sizes as small as 100 μm within a volume of ∼1.5 m3 could be recorded with good contrast, improving the resolution over the standard optics by a factor of four.

From an exposure of the Fermilab 15-foot bubble chamber to the Tevatron quadrupole triplet neutrino beam, we have determined the ratio of neutral-current (NC) to charged-current (CC) interactions to be 0.288 +/- 0.032 for events with visible hadron momentum above 10 GeV/c. The mean nu (nuBAR) event energy is 150 (110) GeV, which is higher than that for any previous beam. This result agrees with those from previous experiments at lower energies. The NC/CC ratio is derived for a combined sample of nu and nuBAR events. A value of 0.274 +/- 0.038 is obtained for the dominant nu-component assuming nuBAR NC/CC = 0.39 +/- 0.08. For events with visible hadron momentum above 25 GeV/c, where the neutral hadron contamination remaining in the NC sample is assumed to be negligible, the combined NC/CC is 0.323 +/- 0.025 and the K0 production rates are 0.375 +/- 0.064 per CC and 0.322 +/- 0.073 per NC event. The corresponding LAMBDA-rates are 0.161 +/- 0.030 per CC and 0.113 +/- 0.030 per NC event. The K0 and LAMBDA-distributions of the fractional hadron energy variable z in NC events are consistent with those in CC events.

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.

During a quadrupole-triplet neutrino experiment with the 15-Foot Bubble Chamber at Fermilab, a large number of events was recorded on approximately 110 000 good holograms, which were taken simultaneously with the conventional three-view photographs. The holograms allow the study of event vertices in a large volume with greatly improved resolution. The experimental setup and the operation of the system is described. Preliminary results obtained during the replay of holograms with the newly developed real- and virtual-image machines are discussed.

The Fermilab 15-ft bubble chamber has been exposed to a quadrupole triplet neutrino beam produced at the Tevatron. The ratio of ν to ν¯ in the beam is approximately 2.5. The mean event energy for ν-induced charged-current events is 150 GeV, and for ν¯-induced charged-current events it is 110 GeV. A total of 64 dimuon candidates (1 μ+μ+, 52 μ−μ+ and μ+μ−, and 11 μ−μ−) is observed in the data sample of approximately 13 300 charged-current events. The number and properties of the μ−μ− and μ+μ+ candidates are consistent with their being produced by background processes, the important sources being π and K decay and punchthrough. The 90%-C.L. upper limit for μ−μ−/μ− for muon momenta above 4 GeV/c is 1.2×10−3, and for momenta above 9 GeV/c this limit is 1.1×10−3. The opposite-sign-dimuon–to–single-muon ratio is (0.62±0.13)% for muon momenta above 4 GeV/c. There are eight neutral strange particles in the opposite-sign sample, leading to a rate per dimuon event of 0.65±0.29. The opposite-sign-dimuon sample is consistent with the hypothesis of charm production and decay.Received 27 September 1989DOI:https://doi.org/10.1103/PhysRevD.41.2057©1990 American Physical Society

The Fermilab 15′ Bubble Chamber, exposed to a beam of neutrinos generated at the Fermilab Tevatron, has been equipped with holographic optics in order to provide a high resolution view of particle interactions over a volume of several m3. A mahine, “HOLRED”, has been constructed to replay the holograms recorded. The principles of the machine and aspects of its construction and operation are described. Results are presented comparing holographic and conventional recordings of neutrino interactions.

Coherent single-pion production on neon nuclei is studied using the Fermilab 15-ft bubble chamber filled with a heavy Ne-${\mathrm{H}}_{2}$ mixture and exposed to the Tevatron neutrino beam. In the neutrino energy range 40--300 GeV, the net signal is 20\ifmmode\pm\else\textpm\fi{}6 events, giving a corrected rate per charged-current event of (0.26\ifmmode\pm\else\textpm\fi{}0.10)%. The cross section and kinematic distributions agree with the predictions of a model based on partial conservation of axial-vector current and meson dominance.

Holography in combination with conventional photography offers the possibility of measuring rare interactions with short lifetimes in large detectors. First experience has been gained with a modified in-line holographic technique during an exposure of the Fermilab 15-Foot Bubble Chamber to a wide-band neutrino beam. Future plans for improvements are outlined.

Plusieurs sources et mécanismes pour la création de bulles dans les liquides surchauffés sont discutés. Les chambres à bulles peuvent être remplies avec une grande variété de liquides, par exemple les liquides cryogéniques hydrogène, deutérium, néon, argon et azote, des mélanges néon/hydrogène et argon/azote, ou les liquides " chauds " propane et divers Fréons® comme le Fréon-13B1®. L'état surchauffé est généralement obtenu par un mouvement rapide d'un piston ou d'une membrane, mais il peut aussi être produit par des ondes ultrasoniques, de choc, ou en mettant les liquides sous tension. La formation des bulles peut être initiée par les particules ionisantes, la lumière (laser) intense ou sur les surfaces rugueuses. La création de bulles embryonnaires n'est pas complètement connue, mais la croissance macroscopique et la condensation peuvent être calculées, permettant l'estimation de la charge de chaleur dynamique. Various sources and mechanisms for bubble formation in superheated liquids are discussed. Bubble chambers can be filled with a great variety of liquids, such as e.g. the cryogenic liquids hydrogen, deuterium, neon, neon/hydrogen mixtures, argon, nitrogen, argon/nitrogen mixtures, or the " warm " liquids propane and various Freon® like Freon-13B1®. The superheated state is normally achieved by a rapid movement of an expansion piston or membrane, but can also be produced by standing ultrasonic waves, shock waves, or putting liquids under tension. Bubble formation can be initiated by ionizing particles, by intense (laser) light, or on rough surfaces. The creation of embryonic bubbles is not completely understood, but the macroscopic growth and condensation can be calculated, allowing to estimate the dynamic heat load.

Recent approaches to solve the solar neutrino problem comprise both new theoretical ideas and newly developed techniques for huge underground detectors. The investigation of electrons produced by neutrinos from the 8B decay is particularly interesting. Earlier bubble chamber photographs of electron tracks (5–20 MeV) in two liquids, the measurements of their energy and direction, may help to optimize the design of these detectors.

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.