Extracted Proton Beam Research Articles

A trigger of events with a high multiplicity of charged particles at the SVD-2 setup

The Thermalization project is currently under way on the extracted proton beam of the U-70 accelerator at the Institute for High Energy Physics. The main goal of this experiment is to study the collective behavior of secondary particles produced in a multiparticle pp interaction at beam energy E = 50–70 GeV. The region of high charged-particle multiplicities nch ≥ 10 is investigated. In this region, a significant portion of energy in the center-of-mass system is dissipated on production of secondary particles, which results in formation of a hadronic system. At the initial instant of evolution, the density of this system is high, which may be responsible for the collective behavior of the secondary particles. The investigations are performed at the SVD-2 wide-aperture magnetic spectrometer. A multichannel trigger scintillation hodoscope used to select rare events with a large number of charged particles exceeding the predetermined value is described. The main flow of low-multiplicity events is suppressed by the trigger system by a factor of ∼102.

Kaon experiments at J-PARC

The newly constructed high-intensity proton synchrotron, J-PARC ( J apan P roton A ccelerator R esearch C omplex), has completed its first stage of construction and started accelerator commissioning. Many experiments using slowly extracted proton beam are proposed and being prepared. Among them, two experiments to study Kaon decays, KOTO to search for a K L → π 0 ν ν ¯ decay and TREK for violation of Time-Reversal invariance, are under preparation. In this article, current status of the experiments is reported.

Production of stripper foils by laser ablation of carbon–boron sputter targets

The TRIUMF Applied Technology Group operates several high-power industrial cyclotrons for commercial radioisotope production. Two of these accelerators, TR30-1 and TR30-2, can deliver H – beams of 30 MeV and beam currents in excess of 1000 μA. For many years, in-house produced diamond-like carbon (DLC) foils of approximately 2.0–3.0 μm thickness have been utilized to extract proton beams from these accelerators. The TRIUMF Carbon Foil Laboratory uses pulsed laser deposition to manufacture DLC films in a wide thickness range (10 nm to ∼10 μm). It is known that the quality and the composition of the graphite sputter target used in the laser ablation process has a significant effect on the mechanical properties of the deposited film as well as its durability in ion beams. Encouraged by the findings of Sugai et al. [1], we investigated the production of stripper foils by laser ablation of graphite/boron composites as well as multilayer foils using pure graphite and boron targets.

Radiation-Resistant Magnets for J-PARC

A series of construction works of the radiation resistant magnets for the Japan Proton Accelerator Research Complex (J-PARC) external beam facilities is now at the production and installation stage. The main accelerator of J-PARC is the 50 GeV proton synchrotron (50 GeV-PS). The designed intensity of the extracted proton beam from the 50 GeV-PS is 15 muA, i.e. a beam power of 750 kW. Then the radiation-resistant magnets are the key apparatus to construct the external beam lines and experimental facilities of the J-PARC 50 GeV-PS. The radiation-resistant magnets we have foreseen are approximately 50 magnets with Polyimide resin Insulation (PI) for radiation dose up to 10 Gy, and 20 magnets with completely Mineral Insulation Cable (MIC) for higher radiation dose up to 1011 Gy. Most of those magnets have already been fabricated and are waiting for being installed in primary and secondary beam lines. The installation will be completed by the middle of 2008. All the magnets are placed on the plug-in base assembled with water and electric-power quick disconnect devices. A new remote handling system of beam line magnets named "Chimney" has been developed and employed for magnets placed at the highest radiation area near the production target. The first beam will be introduced to the experimental area by the end of 2008.

Multilayer carbon foils for cyclotron beam extraction

The TRIUMF Applied Technology Group operates high-power industrial cyclotrons for commercial radioisotope production. Two of these cyclotrons, TR30-1 and TR30-2, are capable of accelerating H − ions to an energy of 30 MeV and beam currents in excess of 1000 μA. For many years, amorphous carbon foils of approximately 2.0 μm thickness have been utilized to extract proton beams from these accelerators. Novel multilayer foils consisting of layers of amorphous and diamond-like carbon (DLC) of 2.0±0.2 μm thickness were manufactured in-house by carbon arc and pulsed laser deposition, respectively. In the TR30 cyclotrons, the new composite foils with 25% DLC content show a three times longer lifetime than the purely amorphous foils, while maintaining their excellent physical and mechanical characteristics during irradiation.

Prospects of high energy density physics research using the CERN super proton synchrotron (SPS)

AbstractThe Super Proton Synchrotron (SPS) will serve as an injector to the Large Hadron Collider (LHC) at CERN as well as it is used to accelerate and extract proton beams for fixed target experiments. In either case, safety of operation is a very important issue that needs to be carefully addressed. This paper presents detailed numerical simulations of the thermodynamic and hydrodynamic response of solid targets made of copper and tungsten that experience impact of a full SPS beam comprized of 288 bunches of 450 GeV/c protons. These simulations have shown that the material will be seriously damaged if such an accident happens. An interesting outcome of this work is that the SPS can be used to carry out dedicated experiments to study High Energy Density (HED) states in matter.

The influence of relative humidity on iron corrosion under proton irradiation

With regard to the storage for high-level radioactive waste and the reversible period of a geological repository, the influence of proton irradiation on the indoor atmospheric corrosion of iron has been investigated in relation to the relative humidity (RH) in the atmosphere. Irradiation experiments were performed using a 3-MeV extracted proton beam. Relative humidity varies from 0% to 85%. Before and after each irradiation, the surfaces of the sample were characterised by Rutherford backscattering spectrometry in order to determine oxygen concentrations in the metal. The maximum oxidation rate was observed for 45% RH in air under proton irradiation and was compared with literature data without irradiation where the maximum oxidation rate was observed at 95% RH. The experimental results are discussed on the basis of the Langmuir–Hinshelwood (LH) model: they are explained by the contrast between the adsorption of O 2 and H 2O species on the active cathodic sites of the iron surface and by the formation of H +(H 2O) n .

A compact cost-effective beamline for a PET Cyclotron

Most commercial PET Cyclotrons have targets mounted on or near the main cyclotron vacuum chamber. There is often little or no system capability for centering or focusing the extracted beam on target to achieve maximum production. This paper describes the ion-optics, design and development of a compact cost-effective beamline comprised of low activation and radiation resistant materials. The beamline, complete with suitable diagnostic devices, permits the extracted proton beam to be centered (X–Y steering magnet), and focused (quadrupole doublet) on target eliminating unnecessary beamspill and ensuring high production.

Ion beam analysis of the effect of O2 and H2O on the oxidation of iron under irradiation

In this paper, the role of air humidity on the iron corrosion under irradiation is studied in the context of geological disposal of nuclear wastes. The irradiation experiments are performed at room temperature using a 3MeV extracted proton beam with a 10nA intensity. Different atmospheres are studied: humid air with a relative humidity (RH) fixed at 45%, dry air and a 15N2 atmosphere (45% RH). The hydrogen and oxygen distribution profiles at the iron surface in contact with atmosphere are measured using respectively ERDA (Elastic Recoil Detection Analysis) and RBS (Rutherford Backscattering Spectrometry) analysis. From these experiments it is clearly demonstrated that the coupling of O2+H2O enhances iron oxidation whereas for iron hydrogenation, humidity is sufficient whatever the atmosphere. An interpretation is given, which is based on the reaction mechanisms and the species formed by air ionisation.

Interbunch extinction measurement at the BNL AGS for the KOPIO experiment

The KOPIO experiment at the BNL AGS required an extracted proton beam in which a debunched, coasting beam is forced between empty longitudinal RF buckets to form microbunches. The goal of the measurement described here was to obtain a low background determination of the fraction of protons coming from the AGS slowly extracted beam at times between microbunches (interbunch extinction). The effect on interbunch extinction of variations in the RF cavity voltage, the momentum dispersion of the beam and the main guide field voltage-ripple was studied. It was found that there exists a broad range of operating parameters that could allow the AGS to produce microbunches with the interbunch extinction better than the KOPIO experiment requirement. Results obtained in this study gave interbunch extinctions better than 10 −5 (1%) of KOPIO's upper limit.

External Scanning Proton Microprobe

Mylar and/or 5 µm-thick polycarbonate foils were mainly used for the window. The foils also play the role of sample backing to minimize the distance between the window and the samples. A window is attached on each sample holder, which is an annular disk made by acrylic resin; the tapered hole has a 1.2 mm diameter on the atmospheric side. Samples are set on holders; up to six holders can be mounted on the revolving stage. The final resolution of the extracted proton beam can be kept at 1 µm. 2, 5

Measurement of cross sections for gamma transitions induced in excited nuclei by the interaction of 1.1-GeV protons with silicon nuclei

The cross sections for the production of excited nuclei were measured in the reaction 28Si(p, xpyn)A* followed by a gamma transition to a state of lower excitation energy or to the ground state. The experiment was performed in an extracted proton beam from the accelerator of the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The reaction in question was identified by a Ge(Li)-NaI(Tl) anticoincidence spectrometer that recorded prompt gamma radiation emitted by the excited final nucleus. The sensitivity of the experiment was 1.5 mb. The cross-section values were obtained for 24 gamma transitions in 17 nuclear products. The cross sections for spallation reactions were estimated. A comparison was performed with known experimental data and with the results of calculations by a semiempirical formula, as well as with the results obtained by simulating hadron interactions on the basis of the GEANT and INUCL codes.

Proton-proton interaction with high multiplicity at energy of 70 GeV (proposal)

The goal of the proposed experiment is to investigate the collective behavior of particles in the process of multiple hadron production in pp interaction pp → n π π + 2N at the beam energy Elab = 70 GeV. The domain of high multiplicity n π = 30–40, or z = n/\(\bar n\) = 4–6, will be studied. Near the threshold of reaction n π → 69, z → zth = 8.2, all particles acquire small relative momentum Δq < 1/R, where R is the dimension of the particle production region. As a consequence of multiboson interference, a number of collective effects may show up: (a) a drastic increase in the partial cross section σ(n) of production of n identical particles is expected, compared with commonly accepted extrapolation; (b) the formation of jets consisting of identical particles may occur as a result of the multiboson Bose-Einstein correlation (BEC) effect; (c) a large fluctuation of charged n(π+,π−) and neutral n(π0) components and onset of centauros or chiral condensate effects are anticipated; (d) an increase in the rate of direct γ as a result of the bremsstrahlung in the partonic cascade and annihilation of π+π− → nγ in dense and cold pionic gas or condensate is expected. In the domain of high multiplicity z ≥ 5, a major part of the c.m. energy \(\sqrt s = 11.6\) GeV is materialized, leading to a high-density thermalized hadronic system. Under this condition, a phase transition to cold quark-gluon plasma (QGP) may occur. The search for QGP signatures like large intermittency in the phase-space particle distribution and an enhanced rate of direct photons will be performed. The experimental setup is designed for detection of rare high-multiplicity events. The experiment is to be carried out at the extracted proton beam of the IHEP U-70 accelerator. The required beam intensity is ∼107 s−1. Under the assumption that the partial cross section σ(n π = 35) = 10-1 nb, the anticipated counting rate is 10-1 events/h. The multiboson BEC enhancement may drastically increase the counting rate.

Characterization of thick graded Si 1− xGe x/Si layers grown by low energy plasma enhanced chemical vapour deposition

Thick, linearly graded-composition strained Si 1− x Ge x /Si layers were recently developed for proton beam bending and extraction experiments. Such unrelaxed layers which are many microns thick necessitate a low maximum germanium content. Here, graded Si 1− x Ge x epilayers, 5–20 μm thick with maximum Ge compositions of x=0.5–1.7%, grown by low energy plasma enhanced chemical vapour deposition were characterized using a recently developed mode of ion channeling analysis which is capable of quantifying the small lattice rotations along off-normal planar directions. High-quality 10 μm Si 1− x Ge x epilayers with bend angles along off-normal directions which agree very well with those of fully strained layers are successfully grown.

Studying a Mode of Intense Proton Beam Extraction by a Bent Crystal with Simultaneous Operation with Internal Targets on the U-70 IHEP Accelerator

A method for extracting a proton beam from the U-70 IHEP synchrotron using a bent silicon crystal at a simultaneous operation of several internal targets is described. The optimal range of the crystal bending angles is 0.5–2.5 mrad, and the crystal length along the beam is 2–5 mm. The extracted-beam intensity can be varied from 107 to 6.0 × 1011 protons per cycle of the U-70 operation, depending on the requirements of physical experimental installations. The method developed for the accelerated-beam extraction with the use of short crystals significantly extends the possibilities of conducting physical experiments on the accelerator.

On the energy dependence of proton beam extraction with a bent crystal

Proton beam extraction from the CERN SPS by means of a bent silicon crystal is reported at three different energies, 14 GeV, 120 GeV and 270 GeV. The experimental results are compared to computer simulations which contain a sound model of the SPS accelerator as well as the channeling phenomena in bent crystals. The overall energy dependence of crystal assisted proton beam extraction is understood and provides the basis to discuss such a scheme for future accelerators.

Optical design of beam lines at the KEK-PS new experimental hall

A new counter experimental hall [K.H. Tanaka et al., IEEE Trans. Magn. 28 (1992) 697] was designed and constructed at the KEK 12-GeV Proton Synchrotron (KEK-PS). The extracted proton beam from the KEK-PS is introduced to the new hall through the newly-prepared primary beam line, EP1, and hits two production targets in cascade. The upstream target provides secondary particles to the low momentum ( 0.4–0.6 GeV c ) separated beam line, K5, and the downstream target is connected to the medium momentum (0.6–2.0 GeV/ c) separated beam line, K6. Several new ideas were employed in the beam optical designs of EP1, K5 and K6 in order to increase the number and the purity of the short-lived secondary particles, such as kaons and pions, under the limited energy and intensity of the primary protons provided by the KEK-PS. These new ideas are described in this paper as well as the first commissioning results.

High efficiency multi-pass proton beam extraction with a bent crystal at the SPS

Recent measurements of 120 GeV proton extraction by means of a bent silicon crystal at the CERN-SPS accelerator are summarized. The existence of multi-pass extraction has been proven by blocking first-pass extraction: using a crystal covered with an amorphous layer, extracted beam with high efficiency was observed, which provides a direct proof for the importance of the multi-pass mechanism. This opens new possibilities in the design and optimization of a bent crystal extraction scheme.

Influence of the thin internal target on the bent crystal extraction efficiency

An attempt to explain the effect of extraction efficiency increase due to thin internal target during proton beam extraction by a bent crystal was made, and results of computer simulation of the thin target influence on the beam parameters in our experiment are given.

Extraction of the 70 GeV proton beam from the IHEP accelerator towards beam line 2(14) with a bent single crystal

The multiturn 70 GeV proton beam extraction towards beam line 2(14) for the PROZA facility with a single crystal of Si bent by 80 mrad installed into the IHEP accelerator vacuum chamber is realized. When (2–3)×10 10 accelerated protons were spilled onto the crystal, about 2 × 10 6 particles were recorded in the beam line. Thus, the extracting efficiency is about 0.8 × 10 −4 by an extracting time of up to 2 s. The possibilities for increasing the extracting efficiency as well as the simultaneity coefficient of the physical facilities are discussed.