Future High-energy Accelerators Research Articles

Stable generation of GeV-class electron beams from self-guided laser–plasma channels

Table-top laser-driven plasma accelerators are gaining attention for their potential use in miniaturizing future high-energy accelerators. By irradiating gas jet targets with ultrashort intense laser pulses, the generation of quasimonoenergetic electron beams was recently observed. Currently, the stability of beam generation and the ability to scale to higher electron beam energies are critical issues for practical laser acceleration. Here, we demonstrate the first generation of stable GeV-class electron beams from stable few-millimetre-long plasma channels in a self-guided wakefield acceleration process. As primary evidence of the laser wakefield acceleration in a bubble regime, we observed a boost of both the electron beam energy and quality by reducing the plasma density and increasing the plasma length in a 1-cm-long gas jet. Subsequent three-dimensional simulations show the possibility of achieving even higher electron beam energies by minimizing plasma bubble elongation, and we anticipate dramatic increases in beam energy and quality in the near future. This will pave the way towards ultracompact, all-optical electron beam accelerators and their applications in science, technology and medicine.

The DREAM Project—Results and plans

High-precision jet spectroscopy will be increasingly important in future high-energy accelerator experiments, particularly at a Linear e + e - Collider. DREAM, a novel type of calorimeter, appears to be well suited for this task. The key aspect of this detector is the simultaneous measurement of the scintillation light and the Cherenkov light generated in the shower development process. By comparing these two signals (which are provided by different types of optical fibers), the electromagnetic shower fraction can be measured event by event, both for single hadrons and for jets, and the effects of fluctuations in this fraction can be eliminated. As a result, the DREAM calorimeter has impressive performance characteristics. The application of the DREAM principles in homogeneous calorimeters, which has the potential of providing ultimate calorimeter performance, is also discussed.

The origin of mass and experiments on future high-energy accelerators

The observable world is the one consisting of nucleons and electrons. The mass of the nucleon arises from chiral symmetry breaking in quantum chromodynamics (QCD), so that high-energy accelerator experiments cannot give any clues to the nature of the mass of matter in the observable world. The origin of the mass of matter will be clarified when the mechanism of chiral symmetry breaking in QCD will be established.

Impact of 24-GeV Proton Irradiation on 0.13-$mu$m CMOS Devices

We studied the response of a commercial 0.13-mum CMOS technology to high-energy (24-GeV) proton irradiation, which emulated the environment the front-end electronics of future high-energy accelerators will have to operate in, for fluences up to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> p/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2 </sup> . After irradiation, large negative shifts in the threshold voltage and large drops in the maximum transconductance were observed in PMOSFETs, whereas comparatively smaller effects were present in NMOSFETs. Furthermore, both kinds of devices exhibited an increase in the drain off-current and in the gate leakage current. All the observed effects were roughly proportional to the proton fluence. For the PMOSFETs only, the amount of the degradation depended on the device channel length. The changes in the characteristics of the irradiated devices were attributed to the build-up of positive charge in the LDD spacer oxide and to the creation of defects in the gate oxide

High-performance computing in accelerating structure design and analysis

Future high-energy accelerators such as the Next Linear Collider (NLC) will accelerate multi-bunch beams of high current and low emittance to obtain high luminosity, which put stringent requirements on the accelerating structures for efficiency and beam stability. While numerical modeling has been quite standard in accelerator R&D, designing the NLC accelerating structure required a new simulation capability because of the geometric complexity and level of accuracy involved. Under the US DOE Advanced Computing initiatives (first the Grand Challenge and now SciDAC), SLAC has developed a suite of electromagnetic codes based on unstructured grids and utilizing high-performance computing to provide an advanced tool for modeling structures at accuracies and scales previously not possible. This paper will discuss the code development and computational science research (e.g. domain decomposition, scalable eigensolvers, adaptive mesh refinement) that have enabled the large-scale simulations needed for meeting the computational challenges posed by the NLC as well as projects such as the PEP-II and RIA. Numerical results will be presented to show how high-performance computing has made a qualitative improvement in accelerator structure modeling for these accelerators, either at the component level (single cell optimization), or on the scale of an entire structure (beam heating and long-range wakefields).

Whispering-Gallery-Mode Resonances: A New Way to Accelerate Charged Particles

Looking for future high energy accelerators we point at a very strong interaction between relativistic electrons and powerful electromagnetic fields existing in the vicinity of a dielectric cylinder in conditions of resonantly excited whispering gallery modes (WGM). A particular example of the WGM resonance, corresponding to angular index n=22, shows that the accelerating fields are almost 100 times stronger than these in the incident wave. That yields an acceleration rate of about 5 GeV/m with the incident microwave radiation beam of the wavelength lambda=1 cm and a moderately high intensity of P=1 MW/cm2.

Advanced accelerator simulation research: miniaturizing accelerators from kilometers to meters

Advanced accelerator research is aimed at finding new technologies that can dramatically reduce the size and cost of future high-energy accelerators. Supercomputing is already playing a dramatic and critical role in this quest. One of the goals of the SciDAC Accelerator Modeling Project is to develop code and software that can ultimately be used to discover the underlying science of new accelerator technology and then be used to design future high-energy accelerators with a minimum amount of capital expenditure on large-scale experiments. We describe the existing hierarchy of software tools for modelling advanced accelerators, how these models have been validated against experiment, how the models are benchmarked against each other, and how these tools are being successfully used to elucidate the underlying science.

Verifiable origin of neutrino mass at TeV scale

The physics responsible for neutrino mass may reside at or below the TeV energy scale. The neutrino mass matrix in the (ν eν μν gt) basis may then be deduced from future high-energy accelerator experiments. The newly observed excess in the muon anomalous magnetic moment may also be related.

The performance of BSCCO racetrack coils at 4.2 K

Small racetrack shaped coils have been fabricated from commercial 2223 and 2212 BSCCO tape conductors and tested in liquid helium at 4.2 K. These coils are insulated with Kapton film and provided with an array of voltage taps so that the characteristics of both straight and curved elements can be examined at various positions in the windings. The performance of the coils is compared to short sample measurements of the conductor. These small coils are prototypes of longer units which will be used in a test magnet designed to explore the potential of high temperature materials for the construction of dipoles and quadrupoles for future high energy accelerators and colliders.

Laser accelerator developments for future high-energy accelerators

Laser-driven accelerators will be realized as the next generation particle accelerators in the near future. Their development has been accelerated by success of high-energy gain electron acceleration by means of a laser wakefield excited via interaction of intense ultrashort laser pulses with underdense plasmas. On the basis of achievements of laser wakefield acceleration (LWFA) experiments, a design of LWFA for the second-generation study is considered from the point of view of application to high-energy accelerators, such as future linear colliders.

Responses of alanine dosimeters to irradiations at cryogenic temperatures

Present and future high-energy accelerators and particle detectors use and will use super-conducting technologies where components are submitted to radiation in a cryogenic environment. Radiation tests and dosimetry calibration have to be made under these conditions. Alanine-ESR dosimetry is world-wide recognised as a standard method for high-dose measurements at room-temperature irradiation. From earlier work, the system also seems suitable for low-temperature applications, despite a decrease of sensitivity. The aim of the present work was to estimate the temperature dependence of five different alanine based dosimeters. The dose-response functions at 290, 77 and 5 K were determined between 10 Gy and 80 kGy. All the results were consistent among the five laboratories: at a given dose, the amplitude of the ESR signal decreases with the irradiation temperature, moreover, this effect is found to be dose-dependent.

Effects of deep level defects in semiconductor detectors

Initiated by the application of semiconductors in the very high radiation environment of future high energy accelerators a formalism has been developed which, based on first principles, allows a quantitative prediction of macroscopic detector behaviour from microscopic defect properties and concentrations. It can be applied also for a systematic study of defect properties by means of measurements of macroscopic material properties. The relation between macroscopic and microscopic properties is developed successively for thermal equilibrium conditions, the fully depleted space charge region, the stationary situation and the general time dependent case. A one dimensional numerical simulation program provides several illustrative results.

NEAR FUTURE PROSPECTS OF QCD SPIN STUDIES

We consider the physics motivations and prospects for the study of spin phenomena at future high energy accelerators. The possibilities of using the already operating machines are also discussed. It is emphasized that the present status of QCD spin studies requires a wide range of spin measurements.

Study of neutron damage resistance of some scintillating crystals and associated photodetectors with the nuclear reactor ULYSSE

ABSTRACTRadiation resistance is a mandatory requirement for a major part of the active or passivecomponents of the particle detectors planned for the future high energy accelerator LHC.Ulysse is a training reactor of the Institut National des Sciences et Techniques Nucl éaires (INSTN), in Saclay, and a very suitable tool for testing materials and devicesfor these future large detectors. Its radiation spectrum characteristics are very similarto those expected in these detectors, in terms of spectra of fast neutrons, thermal neutrons and gamma photons, and ratios between those types of radiation.Results are presented on the neutron resistance of two scintillating crystals, candidatesfor electromagnetic calorimetry, cerium fluoride (CeF3) and lead tungstate (PbWO4), and on the behaviour under neutron irradiation of some avalanche photodiodes, currently under development for light detection of these crystals.

Development of 10 T dipole magnets for the Large Hadron Collider

Development of high field dipole model magnets for future high energy accelerators has been carried out as a part of the cooperative accelerator program between CERN and KEK. A single aperture dipole model magnet was completed and tested. The magnet reached 8.0 T at 4.3 K and 9.87 T at 1.8 K. A twin aperture dipole model magnet with an identical coil design is being assembled. The development status and test results are described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Wake field acceleration experiments

Wake field acceleration is one of several new mechanisms under consideration for use in future high energy accelerators as well as in compact linacs. Plasma, cavity structures, and dielectric media can each be used to generate wake fields when excited by the passage of a charged particle bunch. Acceleration of a separate trailing bunch of particles to high energy by these fields is the goal. A novel test facility developed at ANL now enables experimental investigation of many wake field concepts. Acceleration has been measured using several wake field devices, and comparison with theoretical predictions generally agree. Larger scale demonstration is now being planned to better evaluate practical limitations and use of the technique.

Massive Lepton Pair Production in High Energy Hadron-Hadron Scattering

Massive lepton pair production in high energy hadronic collisions is studied in the framework of perturbative QCD. As for the origin of lepton pairs, the Drell-Yan process and the heavy quark pair production followed by the decay into leptons are taken into account. A model is proposed to reproduce existing experimental data. In the same model, predictions are presented for the massive lepton pair continuum spectrum at future accelerator energies. The effect of scaling violation, form of gluon distribution and Z0 boson are discussed in detail. In the region where , the cross section of lepton pair producion by heavy quark pair is found to dominate over that by the Drell-Yan mechanism. This result indicates a possibility for observing a clean signal of gluon-gluon hard collisions in future high energy accelerators.

Tunable X-ray laser from high energy accelerator

Future high energy accelerators are suggested as a source of tunable laser radiation in the X-ray region of the spectrum. The radiation would result from lasing on the Doppler shifted 2p-1s transition in beams of one-electron atoms.