Optical design for increased interaction length in a high gradient dielectric laser accelerator
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43 PARTICLE ACCELERATORS↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The fast non-ferric kicker system for the Muon g–2 Experiment at Fermilab
Here we describe the installation, commissioning, and characterization of the new injection kicker system in the Muon g – 2 Experiment (E989) at Fermilab, which makes a precision measurement of the muon magnetic anomaly. Three Blumlein pulsers drive each of the 1.27-m-long non-ferric kicker magnets, which reside in a storage ring vacuum (SRV) that is subjected to a 1.45 T magnetic field. The new system has been redesigned relative to Muon g – 2 ’s predecessor experiment, and we present those details in this manuscript.
43 PARTICLE ACCELERATORS↗
Optically pumped polarized 3 He ++ ion source development for RHIC/EIC
The proposed polarized 3 He ++ acceleration in RHIC and the future Electron-Ion Collider will require about 2×10 11 ions in the source pulse. A new technique had been proposed for production of high intensity polarized 3 He ++ ion beams. It is based on ionization and accumulation of the 3 He gas (polarized by metastability-exchange optical pumping and in the 5T high magnetic field) in the existing Electron Beam Ion Source (EBIS). A novel 3 He cryogenic purification and storage technique was developed to provide the required gas purity. An original gas refill and polarized 3 He gas injection to the EBIS long drift tubes, (which serves as the storage cell) were developed to ensure polarization preservation. An infrared laser system for optical pumping and polarization measurements in the high 3–5 T field has been developed. The 3 He polarization 80–85% (and sufficiently long ~30 min relaxation time) was obtained in the “open” cell configuration with refilling valve tube inlet and isolation valve closed. The development of the spin-rotator and 3 He 4 He absolute nuclear polarimeter at 6 MeV 3 He ++ beam energy is also presented here in this work.
43 PARTICLE ACCELERATORS↗
Characterization of 4H-SiC Low Gain Avalanche Detectors (LGADs)
4H-SiC Low Gain Avalanche Detectors (LGADs) have been fabricated and characterized. The devices employ a circular mesa design with low-resistivity contacts and an SiO 2 passivation layer. The I–V and C–V characteristics of the 4H-SiC LGADs are compared with complementary 4H-SiC PiN diodes to confirm a high breakdown voltage and low leakage current. Both LGADs and PiN diodes were irradiated with alpha particles from a $^{210}_{84}$Po source. The charge collected by each device was compared, and it was observed that low-gain charge carrier multiplication is achieved in the 4H-SiC LGAD.
43 PARTICLE ACCELERATORS↗
Detector development for Jefferson Lab's 12GeV Upgrade
Jefferson Lab will soon finish its highly anticipated 12 GeV Upgrade. With doubled maximum energy, Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF) will enable a new experimental program with substantial discovery potential, addressing important topics in nuclear, hadronic and electroweak physics. In order to take full advantage of the high energy, high luminosity beam, new detectors are being developed, designed and constructed to fit the needs of different physics topics. The paper will give an overview of various new detector technologies to be used for 12 GeV experiments. It will then focus on the development of two solenoid-based spectrometers, the GlueX and SoLID spectrometers. The GlueX experiment in Hall D will study the complex properties of gluons through exotic hybrid meson spectroscopy. The GlueX spectrometer, a hermetic detector package designed for spectroscopy and the associated partial wave analysis, is currently in the final stage of construction. Hall A, on the other hand, is developing the SoLID spectrometer to capture the 3D image of the nucleon from semi-inclusive processes and to study the intrinsic properties of quarks through mirror symmetry breaking. Such a spectrometer will have the capability to handle very high event rates while still maintaining a large acceptance in the forward region.
43 PARTICLE ACCELERATORS↗
Particle-in-cell techniques for the study of space charge effects in the Advanced Cryogenic Gas Stopper
The Facility for Rare Isotope Beams, FRIB, will significantly increase the rates and varieties of rare isotopes compared to those presently available at existing rare-isotope facilities. The production of stopped beams via the current generation of linear gas stopping devices available is not well matched to the beam intensities that will be available at FRIB. Many experiments that make use of reaccelerated beams, from the ReA facility, greatly benefit from having the highest-intensity, rare-isotope beams possible. Some experiments would also benefit greatly from stopped beams with improved purity. In this paper, the intensity bottlenecks of FRIB’s newest linear gas stopper are studied via experiment and simulation in support of a future detailed conceptual design of a next-generation linear gas stopper that can provide rare-isotope beams with rates of 10^8 pps, a factor of 50 higher than the current state-of-the-art system, with improved beam purity.
43 PARTICLE ACCELERATORS↗
Finite element analysis of the impact of beam heating mode in molten salt corrosion experiments employing simultaneous ion irradiation
Finite element analysis was used to investigate the temperature and stress profiles that develop in 316L stainless steel membranes being irradiated using different proton beam conditions in contact with a molten salt environment. It was shown that in addition to a nonuniform irradiation profile, a focused 2 MeV proton beam leads to very strong temperature and stress gradients in the membrane, introducing highly localized driving forces that complicate and even compromise the integrity and reliability of the experimental results of corrosion studies. Here, the use of a focused beam in corrosion studies can create experimental artifacts that may misrepresent the true corrosion behavior. In contrast, the use of a rastered beam is shown to distribute the protons and resulting radiation damage uniformly across the membrane face, and more importantly, results in temperature and stress profiles that are not only very uniform but are of much lower magnitude. The use of a rastered beam during molten salt corrosion experiments is therefore recommended to achieve uniform damage rates, thereby reducing both gradients and magnitudes of the temperature and stress distributions.
43 - PARTICLE ACCELERATORS↗
A high-precision miniaturized rotating coil transducer for magnetic measurements
A miniaturized Printed Circuit Board (PCB) sensing coil, jointly developed by CERN and Fermilab for measuring the field of small-gap (less than 10 mm) accelerator magnets, is illustrated. A sensing coil array, with a scheme for compensating the main field when measuring the harmonic error components, hosted on a synthetic sapphire-based transducer, is presented. Key innovating features are (i) very-small size, both for the sensing coil array (thickness of 1.380 mm) and for the transducer (overall diameter of 7.350 mm), (ii) metrological performance, namely accuracy (more than five times better than state of the art), and 1-sigma repeatability (ten times better on harmonics with amplitude less than 100 ppm), and (iii) manufacturing technology of both the coil array (13 double layers aligned within 10 μm), and the sapphire support (concentricity, the most important uncertainty source for rotating coils, 3 μm of uncertainty, namely one order of magnitude better than fiberglass support). After stating the measurement problem, the design of the transducer and a case study of a two-layer PCB sensor array are also illustrated. Then, the prototyping and quality control of both the sensor and the transducer are discussed. Furthermore, the calibration and the results obtained with a prototype setup at Fermilab are presented. Finally, in the appendix, the theory of the rotating coil, the sensor geometry, and the harmonic compensation are briefly reviewed for the reader easiness.
06.20.fb/calibration↗
A MHz-repetition-rate hard X-ray free-electron laser driven by a superconducting linear accelerator
The European XFEL is a hard X-ray free-electron laser (FEL) based on a high-electron-energy superconducting linear accelerator. The superconducting technology allows for the acceleration of many electron bunches within one radio-frequency pulse of the accelerating voltage and, in turn, for the generation of a large number of hard X-ray pulses. In this paper, we report on the performance of the European XFEL accelerator with up to 5,000 electron bunches per second and demonstrating a full energy of 17.5 GeV. Feedback mechanisms enable stabilization of the electron beam delivery at the FEL undulator in space and time. The measured FEL gain curve at 9.3 keV is in good agreement with predictions for saturated FEL radiation. Hard X-ray lasing was achieved between 7 keV and 14 keV with pulse energies of up to 2.0 mJ. Using the high repetition rate, an FEL beam with 6 W average power was created.
43 PARTICLE ACCELERATORS↗
The need for reproducible research in soft robotics
In recent years we have witnessed the rise of commercialization efforts for soft robotic technology, including soft grippers (Soft Robotics, Inc.), stretchable sensors (StretchSense, Inc. and Lightlace, Inc.), and platforms for human-robot interaction (Festo Inc., Meta Reality Labs, Toyota Research Institute, and Disney Research). However, commercialization as a whole lags the trends enjoyed by other robotic technology at equivalent points in their respective lifecycles.
43 PARTICLE ACCELERATORS↗
Present and Future X-ray Tomographic Microscopy at TOMCAT
During its first four years of life, the TOMCAT beamline at the Swiss Light Source has established itself as a state-of-the art hard x-ray tomographic microscopy endstation for experiments on a large variety of samples, ranging from the fields of biology to materials science. It routinely performs absorption as well as phase-contrast imaging with an isotropic voxel size ranging from 0.360 up to 14.8 microns. Phase contrast is obtained either with simple edge-enhancement, a modified transport of intensity approach or grating interferometry. Typical acquisition times are on the order of a few minutes, depending on energy and resolution. A recently implemented automatic sample exchanger is now available for high-throughput studies. In addition to further developments in phase-contrast imaging, current scientific activities at the beamline focus on pushing spatial and temporal resolution by a few orders of magnitude, aiming at nano- and 'real-time' tomography.
43 PARTICLE ACCELERATORS↗
A time-of-flight backscattering spectrometer at the Spallation Neutron Source, BASIS
We describe the design and current performance of the backscattering silicon spectrometer (BASIS), a time-of-flight backscattering spectrometer built at the spallation neutron source (SNS) of the Oak Ridge National Laboratory (ORNL). BASIS is the first silicon-based backscattering spectrometer installed at a spallation neutron source. In addition to high intensity, it offers a high-energy resolution of about 3.5 {mu}eV and a large and variable energy transfer range. These ensure an excellent overlap with the dynamic ranges accessible at other inelastic spectrometers at the SNS.
43 PARTICLE ACCELERATORS↗
A solid-state Marx generator driven Einzel lens chopper
A new type of pulse chopper called an Einzel lens chopper is described. An Einzel lens placed immediately after an electron cyclotron resonance ion source is driven by high-voltage pulses generated by a newly developed solid-state Marx generator. A rectangular negative barrier pulse-voltage is controlled in time, and the barrier pulse is turned on only when a beam pulse is required. The results of successful experiments are reported herein.
43 PARTICLE ACCELERATORS↗
Imaging single electrons to enable the generation of ultrashort beams for single-shot femtosecond relativistic electron diffraction
The generation and control of relativistic electron beams well suited for ultrafast electron diffraction application has rapidly advanced, greatly benefiting from the overlap in techniques and expertise with the accelerator community. However, imaging the diffracted MeV electrons with high detection efficiency has remained an under-explored area. In this paper, we report on a quantitative study of the imaging of MeV electrons using a detection system consisting of a phosphor screen, a lens-coupling optics, and a charge-coupled device camera. It is shown that every MeV electron in the beam yields a signal well above the camera noise. With this detection efficiency, only {approx}10{sup 5} electrons per pulse are needed to obtain a high quality single-shot diffraction pattern from a crystalline sample. We measured that such a low charge beam can be as short as 30 fs rms. Further, we discuss the possibility of compressing these electron beams to sub-5 fs rms bunch length by velocity bunching using a short high gradient rf accelerating structure scheduled to be installed next year at the UCLA Pegasus Laboratory. This opens the possibility of single-shot determinations of structural changes in many ultrafast physical processes like nonequilibrium phonon dynamics or relaxation pathways in systems with strong electron-phonon coupling.
43 PARTICLE ACCELERATORS↗
Extraction of the Compton Form Factor H from DVCS Measurements in the Quark Sector
Working at twist 2 accuracy and assuming the dominance of the Generalized Parton Distribution H we study the helicity-dependent and independent cross sections measured in Hall A, the beam spin asymmetries measured in Hall B at Jefferson Laboratory and beam charge, beam spin and target spin asymmetries measured by Hermes. We extract the real and imaginary parts of the Compton Form Factor H, the latter being obtained with a 20-50 % uncertainty. We pay extra attention to the estimation of systematic errors on the extraction of H. We discuss our results and compare to other extractions as well as to the popular VGG model.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
A measurement of double spin asymmetry A{sub LT} in semi-inclusive pion electroproduction on a transversely polarized {sup 3}He target
The double spin asymmetry A{sub LT} for {sup 3}He was measured for the first time at Jefferson Lab Hall A in the semi-inclusive {sup 3}He{up_arrow}({sup {yields}e},{pi}{sup +/-}X reactions, using a 6 GeV polarized electron beam on a transversely polarized {sup 3}He target. The produced charged pions were detected in coincidence with the scattered electrons by the high-resolution spectrometer and the BigBite spectrometer, respectively. The kinematic coverage was focused on the valence quark region, x {approx} 0.13-0.41, Q{sup 2}{approx} 1.31-3.10 (GeV/c){sup 2}. When combined with the world data, this new data will provide constraints on the g{sub 1T}{sup q} distribution functions, which describe the longitudinal polarization of quarks in a transversely polarized nucleon. The status of the current analysis and the preliminary results are presented.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Spin physics with CLAS and CLAS12
An extensive experimental program to measure the spin structure of the nucleon has been conducted in Hall B at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) in the last decade. Using a longitudinally polarized beam scattering off longitudinally polarized NH{sub 3} and ND{sub 3} targets, inclusive Deep Inelastic Scattering (DIS), Semi-Inclusive DIS (SIDIS) and DVCS experiments were carried out that make a significant contributions to the existing data. The inclusive double spin asymmetry A{sub ||} was measured over a large range in Q{sup 2} and W, providing data of impressively high precision that give a better understanding of the structure of the nucleon in the DIS and the valence quarks regions. Using parameterizations A2 and F1 from world data, the virtual photon asymmetry A1 and the structure function g1 were extracted in a Q{sup 2} range from 0.05 to 5 GeV{sup 2} and a W range from 1.08 to 3.0 GeV. As a result of the extended kinematical range, first moments of structure functions were measured over a large range in Q{sup 2} and duality was tested. Furthermore, newly proposed experiments, using an upgraded accelerator at Jefferson Laboratory and an improved CLAS detector (CLAS12), are expected to increase the statistical precision of the current measurements and extend them to kinematic regions presently not accessible, such as high x. This will improve significantly our knowledge of the structure of the nucleon, including parton distribution functions, duality and higher twists contributions.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Calibration method of tilt and azimuth angles for alignment of TEM tomographic tilt series
This paper describes the calibration method of the tilt and azimuth angles of specimen using a digital protractor and a laser autocollimator for alignment of electron tomography. It also suggests an easy method to check whether the specimen is tilted by 180.0 deg., and whether the azimuth angle is 0.0 deg.; the method involves the use of two images of a rod-shaped specimen collected before and after a 180.0 deg. The method is based on the assumption that these images are symmetric about the tilt axis when the azimuth angle is 0.0 deg. In addition, we used an experiment to demonstrate the effect of the incorrect angles on reconstructed images and simulated the image quality against distance away from tilt axis.
43 PARTICLE ACCELERATORS↗