Instruments

25 pages, 23218 KiB

Open AccessArticle

Electric Field Enhancing Artifacts as Precursors for Vacuum High-Voltage Breakdown

by Rolf Behling

Instruments 2019, 3(4), 64; https://doi.org/10.3390/instruments3040064 - 17 Dec 2019

Viewed by 3161

Abrupt formation of plasma in a high-voltage insulating vacuum gap and subsequent discharge of electrodes limits the reliability of a class of vacuum electronic devices, such as X-ray tubes. It has been suggested that electron field emission from negatively charged electrodes would precede [...] Read more.

Abrupt formation of plasma in a high-voltage insulating vacuum gap and subsequent discharge of electrodes limits the reliability of a class of vacuum electronic devices, such as X-ray tubes. It has been suggested that electron field emission from negatively charged electrodes would precede and initiate such discharge. Heating and evaporation of material upon field emission would cause dense plasma to develop in periods of nanoseconds. High-pressure plasma would expand from the cathode, eventually bridging the gap. Nevertheless, the very reason for the unredictable initial development of discharge events after long periods of reliable operation is still matter of debate. Experience from industrial processes suggests hydrocarbon contamination to degrade the electric stability of high-voltage gaps. While former attempts aimed at explaining high field emission by carbonaceous 2D structures or surface resonance effects, this paper discusses whether 3D structures may grow slowly, until their evaporation in a matter of nanoseconds. Similar to the production of carbon nanotubes, protruding structures might comprise carbon and, in addition, metallic nanoparticles, which would boost production of vapor during their explosion. The hypothesis was tested by scanning electron and energy-dispersive X-ray inspection of two cathodes of medical X-ray tubes, covered with metallic seed nanoparticles, which served as model systems. A third cleaner cathode was inspected for comparison. Although certain suggested conditions of carbon feed, elevated substrate temperature and nanoparticle contamination of the surfaces were met, images showed only a very weak sign of growth of suspicious carbon structures. It seems, therefore, unlikely that CNT-like structures are a major cause of high-voltage breakdown between electrodes of X-ray tubes. Full article

► Show Figures

Figure 1

7 pages, 2422 KiB

Open AccessFeature PaperArticle

Study of the Extracted Beam Energy as a Function of Operational Parameters of a Medical Cyclotron

by Philipp Häffner, Carolina Belver Aguilar, Saverio Braccini, Paola Scampoli and Pierre Alexandre Thonet

Instruments 2019, 3(4), 63; https://doi.org/10.3390/instruments3040063 - 05 Dec 2019

Cited by 15 | Viewed by 2722

Abstract

The medical cyclotron at the Bern University Hospital (Inselspital) is used for both routine

^{18}

F production for Positron Emission Tomography (PET) and multidisciplinary research. It provides proton beams of variable intensity at a nominal fixed energy of 18 MeV. Several scientific activities, [...] Read more.

The medical cyclotron at the Bern University Hospital (Inselspital) is used for both routine

^{18}

F production for Positron Emission Tomography (PET) and multidisciplinary research. It provides proton beams of variable intensity at a nominal fixed energy of 18 MeV. Several scientific activities, such as the measurement of nuclear reaction cross-sections or the production of non-conventional radioisotopes for medical applications, require a precise knowledge of the energy of the beam extracted from the accelerator. For this purpose, a study of the beam energy was performed as a function of cyclotron operational parameters, such as the magnetic field in the dipole magnet or the position of the extraction foil. The beam energy was measured at the end of the 6 m long Beam Transfer Line (BTL) by deflecting the accelerated protons by means of a dipole electromagnet and by assessing the deflection angle with a beam profile detector. Full article

► Show Figures

Figure 1

27 pages, 908 KiB

Open AccessArticle

Dipole Magnets above 20 Tesla: Research Needs for a Path via High-Temperature Superconducting REBCO Conductors

by Xiaorong Wang, Stephen A. Gourlay and Soren O. Prestemon

Instruments 2019, 3(4), 62; https://doi.org/10.3390/instruments3040062 - 22 Nov 2019

Cited by 27 | Viewed by 4929

Abstract

To enable the physics research that continues to deepen our understanding of the Universe, future circular colliders will require a critical and unique instrument—magnets that can generate a dipole field of 20 T and above. However, today’s maturing magnet technology for low-temperature superconductors [...] Read more.

To enable the physics research that continues to deepen our understanding of the Universe, future circular colliders will require a critical and unique instrument—magnets that can generate a dipole field of 20 T and above. However, today’s maturing magnet technology for low-temperature superconductors (Nb-Ti and Nb₃Sn) can lead to a maximum dipole field of around 16 T. High-temperature superconductors such as REBCO can, in principle, generate higher dipole fields but significant challenges exist for both conductor and magnet technology. To address these challenges, several critical research needs, including direct needs on instrumentation and measurements, are identified to push for the maximum dipole fields a REBCO accelerator magnet can generate. We discuss the research needs by reviewing the current results and outlining the perspectives for future technology development, followed by a brief update on the status of the technology development at Lawrence Berkeley National Laboratory. We present a roadmap for the next decade to develop 20 T-class REBCO accelerator magnets as an enabling instrument for future energy-frontier accelerator complex. Full article

(This article belongs to the Special Issue Applied Superconductivity for Particle Accelerator)

► Show Figures

Figure 1

12 pages, 49583 KiB

Open AccessArticle

Molybdenum Oxides Coatings for High Demanding Accelerator Components

by Jessica Scifo, Augusto Marcelli, Bruno Spataro, Dariush Hampai, Sultan Dabagov, Stefano Sarti, Antonio Di Trolio, Riccardo Moscatelli, Salvatore Macis and Luigi Faillace

Instruments 2019, 3(4), 61; https://doi.org/10.3390/instruments3040061 - 12 Nov 2019

Cited by 3 | Viewed by 2770

Abstract

Large electric gradients are required for a variety of new applications, notably including the extreme high brightness electron sources for X-ray free electron lasers (FELs), radio-frequency (RF) photo-injectors, industrial and medical accelerators, and linear accelerators for particle physics colliders. In the framework of [...] Read more.

Large electric gradients are required for a variety of new applications, notably including the extreme high brightness electron sources for X-ray free electron lasers (FELs), radio-frequency (RF) photo-injectors, industrial and medical accelerators, and linear accelerators for particle physics colliders. In the framework of the INFN-LNF, SLAC (USA), KEK (Japan), UCLA (Los Angeles) collaboration, the Frascati National Laboratories (LNF) are involved in the modelling, development, and testing of RF structures devoted to particles acceleration by high gradient electric fields of particles through metal devices. In order to improve the maximum sustainable gradients in normal-conducting RF-accelerating structures, both the RF breakdown and dark current should be minimized. To this purpose, studying new materials as well as manufacturing techniques are mandatory to identify better solutions to such extremely requested applications. In this contribution, we discuss the possibility of using a dedicated coating on a solid copper sample (and other metals) with a relatively thick film to improve and optimize breakdown performances and to minimize the dark current. We present here the first characterization of MoO₃ films deposited on copper by pulsed-laser deposition (PLD). Full article

(This article belongs to the Special Issue Physics and Applications of High Brightness Beams)

► Show Figures

Figure 1

5 pages, 204 KiB

Open AccessEditorial

Special Issue ”Instruments and Methods for Cyclotron Produced Radioisotopes”

by Saverio Braccini and Francisco Alves

Instruments 2019, 3(4), 60; https://doi.org/10.3390/instruments3040060 - 08 Nov 2019

Cited by 2 | Viewed by 2518

Abstract

The 17th Workshop on Targets and Target Chemistry (WTTC17) was held in Coimbra (Portugal) on 27–31 August 2018. A few months before, the 13th Workshop of the European Cyclotron Network (CYCLEUR) took place in Lisbon (Portugal) on 23–24 November 2017. These two events [...] Read more.

The 17th Workshop on Targets and Target Chemistry (WTTC17) was held in Coimbra (Portugal) on 27–31 August 2018. A few months before, the 13th Workshop of the European Cyclotron Network (CYCLEUR) took place in Lisbon (Portugal) on 23–24 November 2017. These two events reassembled major experts in the field of radioisotope production, targets, target chemistry and cyclotrons. In the last few years, significant advances have been obtained in these fields with direct implications for science and society. Instruments and methods, originally developed for nuclear and particle physics, played a crucial role and remarkable developments are on-going. The production of novel radioisotopes for both diagnostics and therapy is expected to produce a breakthrough in nuclear medicine in the next years, paving the way towards theranostics and personalized medicine. This Special Issue presents a collection of original scientific contributions on the latest developments on instruments and methods for medical and research cyclotrons as well as on target and target chemistry for the production of radioisotopes. Full article

(This article belongs to the Special Issue Instruments and Methods for Cyclotron Produced Radioisotopes)

11 pages, 3795 KiB

Open AccessArticle

1D Quantum Simulations of Electron Rescattering with Metallic Nanoblades

by Joshua Mann, Gerard Lawler and James Rosenzweig

Instruments 2019, 3(4), 59; https://doi.org/10.3390/instruments3040059 - 05 Nov 2019

Viewed by 3516

Abstract

Electron rescattering has been well studied and simulated for cases with ponderomotive energies of the quasi-free electrons, derived from laser–gas and laser–surface interactions, lower than 50 eV. However, with advents in longer wavelengths and laser field enhancement metallic surfaces, previous simulations no longer [...] Read more.

Electron rescattering has been well studied and simulated for cases with ponderomotive energies of the quasi-free electrons, derived from laser–gas and laser–surface interactions, lower than 50 eV. However, with advents in longer wavelengths and laser field enhancement metallic surfaces, previous simulations no longer suffice to describe more recent strong field and high yield experiments. We present a brief introduction to and some of the theoretical and empirical background of electron rescattering emissions from a metal. We set upon using the Jellium potential with a shielded atomic surface potential to model the metal. We then explore how the electron energy spectra are obtained in the quantum simulation, which is performed using a custom computationally intensive time-dependent Schrödinger equation solver via the Crank–Nicolson method. Finally, we discuss the results of the simulation and examine the effects of the incident laser’s wavelength, peak electric field strength, and field penetration on electron spectra and yields. Future simulations will investigate a more accurate density functional theory metallic model with a system of several non-interacting electrons. Eventually, we will move to a full time-dependent density functional theory approach. Full article

(This article belongs to the Special Issue Physics and Applications of High Brightness Beams)

► Show Figures

Figure 1

8 pages, 3051 KiB

Open AccessArticle

Design of Comb Fabricated Halbach Undulators

by Nathan Majernik and James Rosenzweig

Instruments 2019, 3(4), 58; https://doi.org/10.3390/instruments3040058 - 19 Oct 2019

Cited by 8 | Viewed by 3071

Abstract

An approach to fabricating Halbach array undulators using “combs” machined from single magnets is introduced. This technique is especially relevant to the fabrication of short period micro-undulators with period lengths considerably less than the few-centimeter-scale typical of current undulators. Manual, magnet-by-magnet assembly of [...] Read more.

An approach to fabricating Halbach array undulators using “combs” machined from single magnets is introduced. This technique is especially relevant to the fabrication of short period micro-undulators with period lengths considerably less than the few-centimeter-scale typical of current undulators. Manual, magnet-by-magnet assembly of micro-undulators would require the manipulation and alignment of thousands of magnets smaller than a grain of rice: comb fabrication dramatically increases the size of the basic unit cell of assembly with no increase in undulator period by creating many periods from a single piece, in a single machining modality. Further, as these comb teeth are intrinsically indexed to each other, tolerances are dictated by a single manufacturing step rather than accumulating errors by assembling many tiny magnets relative to each other. Different Halbach geometries, including

M^{'} = 2

,

M^{'} = 4

, isosceles triangle, and hybrid, are examined both from a theoretical perspective and with 3D magnetostatic simulations. Full article

(This article belongs to the Special Issue Physics and Applications of High Brightness Beams)

► Show Figures

Figure 1

12 pages, 2512 KiB

Open AccessArticle

Electron Diagnostics for Extreme High Brightness Nano-Blade Field Emission Cathodes

by Gerard Lawler, Kunal Sanwalka, Yumeng Zhuang, Victor Yu, Timo Paschen, River Robles, Oliver Williams, Yusuke Sakai, Brian Naranjo and James Rosenzweig

Instruments 2019, 3(4), 57; https://doi.org/10.3390/instruments3040057 - 16 Oct 2019

Cited by 1 | Viewed by 4732

Abstract

Electron beams are essential tools in modern science. They are ubiquitous in fields ranging from microscopy to the creation of coherent ultra-fast X-rays to lithography. To keep pace with demand, electron beam brightness must be continually increased. One of the main strategic aims [...] Read more.

Electron beams are essential tools in modern science. They are ubiquitous in fields ranging from microscopy to the creation of coherent ultra-fast X-rays to lithography. To keep pace with demand, electron beam brightness must be continually increased. One of the main strategic aims of the Center for Bright Beams (CBB), a National Science Foundation Science and Technology Center, is to increase brightness from photocathodes by two orders of magnitude. Improving the state-of-the-art for photoemission-based cathodes is one possibility. Several factors have led to an alternative design becoming an increasing necessity; the nanoscale structure. Field emission sources from nano-tips would be an ideal candidate were it not for their low current and damage threshold. A 1-dimensional extended nano-fabricated blade, i.e., a projected tip, can solve the problems inherent in both designs. The novel geometry has been demonstrated to produce extremely high brightness electron beam bunches and is significantly more robust and easier to manufacture than traditional photocathodes. Theory indicates electron emission up to keV energies. We thus present a system of diagnostics capable of analyzing the cathodes and assessing their viability. The diagnostics are designed to measure the electron spectrum up to keV energies, with sub meV resolution at <100 eV, mean transverse energy (MTE), emission uniformity, and cathode lifetime. We also report preliminary data on total extracted charge and maximum detectable electron energy with a simplified retarding field spectrometer. Full article

(This article belongs to the Special Issue Physics and Applications of High Brightness Beams)

► Show Figures

Figure 1

13 pages, 1435 KiB

Open AccessFeature PaperArticle

Custom Scrubbing for Robust Configuration Hardening in Xilinx FPGAs

by Raffaele Giordano, Dario Barbieri, Sabrina Perrella and Roberto Catalano

Instruments 2019, 3(4), 56; https://doi.org/10.3390/instruments3040056 - 14 Oct 2019

Cited by 8 | Viewed by 3862

Abstract

The usage of SRAM-based Field Programmable Gate Arrays on High Energy Physics detectors is mostly limited by the sensitivity of these devices to radiation-induced upsets in their configuration. These effects may alter the functionality until the next reconfiguration of the device. In this [...] Read more.

The usage of SRAM-based Field Programmable Gate Arrays on High Energy Physics detectors is mostly limited by the sensitivity of these devices to radiation-induced upsets in their configuration. These effects may alter the functionality until the next reconfiguration of the device. In this work, we present the radiation testing of a high-speed serial link hardened by a new, custom scrubber designed for Xilinx FPGAs. We compared the performance of our scrubber to the Xilinx Single Event Mitigation (SEM) controller and we measured the impact of the scrubbers on the reliability of the link. Our results show that our scrubber may improve reliability up to 23 times over the SEM. Full article

► Show Figures

Figure 1

15 pages, 2330 KiB

Open AccessArticle

Capabilities of Terahertz Cyclotron and Undulator Radiation from Short Ultrarelativistic Electron Bunches

by Vladimir Bratman, Yuri Lurie, Yuliya Oparina and Andrey Savilov

Instruments 2019, 3(4), 55; https://doi.org/10.3390/instruments3040055 - 11 Oct 2019

Cited by 6 | Viewed by 2187

Abstract

Mechanisms of coherent spontaneous cyclotron and undulator radiations of short dense bunches, in which electrons move along the same stationary helical trajectories, but have different dynamic properties, have been compared in detail. The results are based on the simplest 1D model in the [...] Read more.

Mechanisms of coherent spontaneous cyclotron and undulator radiations of short dense bunches, in which electrons move along the same stationary helical trajectories, but have different dynamic properties, have been compared in detail. The results are based on the simplest 1D model in the form of a plane consisting of uniformly distributed synchronously moving and in-phase emitting particles, as well as numerical 3D codes developed to study the dynamics of bunches in waveguides taking into account the effects of the radiation and spatial charge fields. For cyclotron radiation under group synchronism conditions, the Coulomb expansion of a bunch occurs along the surface of a constant wave phase with the formation of an effectively radiating coherent structure. A significantly higher radiation frequency, but with a lower efficiency, can be obtained in the regime of simultaneous excitation of high-frequency (autoresonant) and low-frequency waves; in the field of the latter, stabilization of the bunch phase size can be achieved. Such a two-wave generation is much more efficient when the bunches radiate in the combined undulator and strong guiding magnetic fields under conditions of the negative mass instability, when both the Coulomb interaction of the particles and the radiation field stabilize the longitudinal size of the bunch. Full article

(This article belongs to the Special Issue Physics and Applications of High Brightness Beams)

► Show Figures

Figure 1

10 pages, 1264 KiB

Open AccessArticle

GeV-Class Two-Fold CW Linac Driven by an Arc-Compressor

by Alberto Bacci, Angelo Bosotti, Simone Di Mitri, Illya Drebot, Luigi Faillace, Paolo Michelato, Laura Monaco, Michele Opromolla, Rocco Paparella, Vittoria Petrillo, Marcello Rossetti Conti, Andrea Renato Rossi, Luca Serafini and Daniele Sertore

Instruments 2019, 3(4), 54; https://doi.org/10.3390/instruments3040054 - 10 Oct 2019

Cited by 3 | Viewed by 2559

Abstract

We present a study of an innovative scheme to generate high repetition rate (MHz-class) GeV electron beams by adopting a two-pass two-way acceleration in a super-conducting Linac operated in Continuous Wave (CW) mode. The beam is accelerated twice in the Linac by being [...] Read more.

We present a study of an innovative scheme to generate high repetition rate (MHz-class) GeV electron beams by adopting a two-pass two-way acceleration in a super-conducting Linac operated in Continuous Wave (CW) mode. The beam is accelerated twice in the Linac by being re-injected, after the first pass, in opposite direction of propagation. The task of recirculating the electron beam is performed by an arc compressor composed by 14 Double Bend Achromat (DBA). In this paper, we study the main issues of the two-fold acceleration scheme, the electron beam quality parameters preservation (emittance, energy spread), together with the bunch compression performance of the arc compressor, aiming to operate an X-ray Free Electron Laser. The requested power to supply the cryogenic plant and the RF sources is also significantly reduced w.r.t a conventional one-pass SC Linac for the same final energy. Full article

(This article belongs to the Special Issue Physics and Applications of High Brightness Beams)

► Show Figures

Figure 1

10 pages, 10254 KiB

Open AccessFeature PaperArticle

Compression of Ultra-High Brightness Beams for a Compact X-ray Free-Electron Laser

by River Robles and James Rosenzweig

Instruments 2019, 3(4), 53; https://doi.org/10.3390/instruments3040053 - 01 Oct 2019

Cited by 6 | Viewed by 3362

Abstract

The creation of the first X-ray free-electron laser at SLAC in 2009 introduced the scientific community to coherent photons of unprecedented high brightness. These photons were produced, however, at the cost of billion-dollar-class price tags and kilometer-scale machine footprints. This has meant that [...] Read more.

The creation of the first X-ray free-electron laser at SLAC in 2009 introduced the scientific community to coherent photons of unprecedented high brightness. These photons were produced, however, at the cost of billion-dollar-class price tags and kilometer-scale machine footprints. This has meant that getting access to these photons is very difficult, and those who do get access do so with a strict time budget. Now, the development of critical enabling technologies, in particular high-field cryogenically cooled accelerating cavities and short-period, high-field undulator magnets, opens the door to an X-ray free-electron laser less than 30 m in length. We present here critical potential design elements for such a soft X-ray free-electron laser. To this end, simulation results are presented focusing on the problems associated with the process of bunch compression and novel ways in which those problems can be resolved. Full article

(This article belongs to the Special Issue Physics and Applications of High Brightness Beams)

► Show Figures

Figure 1

19 pages, 8763 KiB

Open AccessArticle

High-Brightness Beam Technology Development for a Future Dynamic Mesoscale Materials Science Capability

by Bruce E. Carlsten, Petr M. Anisimov, Cris W. Barnes, Quinn R. Marksteiner, River R. Robles and Nikolai Yampolsky

Instruments 2019, 3(4), 52; https://doi.org/10.3390/instruments3040052 - 29 Sep 2019

Cited by 11 | Viewed by 3493

Abstract

A future capability in dynamic mesoscale materials science is needed to study the limitations of materials under irreversible and extreme conditions, where these limitations are caused by nonuniformities and defects in the mesoscale. This capability gap could potentially be closed with an X-ray [...] Read more.

A future capability in dynamic mesoscale materials science is needed to study the limitations of materials under irreversible and extreme conditions, where these limitations are caused by nonuniformities and defects in the mesoscale. This capability gap could potentially be closed with an X-ray free-electron laser (XFEL), producing 5 × 10¹⁰ photons with an energy of 42 keV, known as the Matter–Radiation Interactions in Extremes (MaRIE) XFEL. Over the last few years, researchers at the Los Alamos National Laboratory have developed a preconceptual design for a MaRIE-class XFEL based on existing high-brightness beam technologies, including superconducting L-band cryomodules. However, the performance of a MaRIE-class XFEL can be improved and the risk of its operation reduced by investing in emerging high-brightness beam technologies, such as the development of high-gradient normal conducting radio frequency (RF) structures. Additionally, an alternative XFEL architecture, which generates a series of high-current microbunches instead of a single bunch with uniformly high current along it, may suppress the most important emittance degradation effects in the accelerator and in the XFEL undulator. In this paper, we describe the needed dynamic mesoscale materials science capability, a MaRIE-class XFEL, and the proposed microbunched XFEL accelerator architecture in detail. Full article

(This article belongs to the Special Issue Physics and Applications of High Brightness Beams)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Instruments, Volume 3, Issue 4 (December 2019) – 13 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI