Emittance growth from modulated focusing and bunched electron beam cooling
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43 PARTICLE ACCELERATORS↗
SEARCH · Engineering Papers
Results for “electronics cooling”
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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SRF and RF systems for LEReC Linac
The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosity at low energies. It will consist of a short electron linac and two cooling sections, one for blue and one for yellow rings. For the first stage of the project, LEReC-I, we will install a 704 MHz superconducting RF cavity and three normal conducting cavities operating at 9 MHz, 704 MHz and 2.1 GHz. The SRF cavity will boost the electron beam energy up to 2 MeV. The warm cavities will be used to correct the energy spread introduced in the SRF cavity. The paper describes layouts of the SRF and RF systems, their parameters and status.
43 PARTICLE ACCELERATORS↗
Dispersion effect on the cooling rates
It is known that dispersion can redistribute the electron cooling rate between longitudinal and transverse planes. This note presents a simple analytical model to explain and estimate this redistribution effect. It shows that a small horizontal dispersion on ions can enhance horizontal cooling at the expense of longitudinal cooling rate. The electron dispersion is also beneficial to this effect.
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Subcooled Boiling Heat Transfer for Cooling of Power Electronics in Hybrid Electric Vehicles
At present, single-phase liquid, forced convection cooled heat sinks with fins are used to cool power electronics in hybrid electric vehicles (HEVs). Although use of fins in the cooling channels increases heat transfer rates considerably, a second low-temperature radiator and associated pumping system are still required in HEVs. This additional cooling system adds weight and cost while decreasing the efficiency of HEVs. With the objective of eliminating this additional low-temperature radiator and pumping system in HEVs, an alternative cooling technology, subcooled boiling in the cooling channels, was investigated in the present study. Numerical heat transfer simulations were performed using subcooled boiling in the power electronics cooling channels with the coolant supplied from the existing main engine cooling system. Results show that this subcooled boiling system is capable of removing 25% more heat from the power electronics than the conventional forced convection cooling technology, or it can reduce the junction temperature of the power electronics at the current heat removal rate. With the 25% increased heat transfer option, high heat fluxes up to 250 W/cm(2) (typical for wideband-gap semiconductor applications) are possible by using the subcooled boiling system.
Heat transfer simulations↗
Cooling Shelf For Electronic Equipment
Heat-pipe action cools and maintains electronics at nearly constant temperature. System designed to control temperatures of spacecraft shelves or baseplates by combining honeycomb sandwich panel with reservoir of noncondensable gas and processing resulting device as variable-conductance heat pipe. Device provides flat surface for mounting heat-dissipating electronics that is effectively cooled and maintained at nearly constant temperature. Potentially useful in freeze drying, refrigeration, and air conditioning.
Tanzer, Herbert J.↗
Gamma-ray burst spectrum with decaying magnetic field
In the internal shock model for gamma-ray bursts (GRBs), the synchrotron spectrum from the fast cooling electrons in a homogeneous downstream magnetic field (MF) is too soft to produce the low-energy slope of GRB spectra. However, the MF may decay downstream with distance from the shock front. Here we show that the synchrotron spectrum becomes harder if electrons undergo synchrotron and inverse-Compton cooling in a decaying MF. To reconcile this with the typical GRB spectrum with low-energy slope νF {sub ν}∝ν, the postshock MF decay time must be comparable to the cooling time of the bulk electrons (corresponding to a MF decaying length typically of ∼10{sup 5} skin depths); that the inverse-Compton cooling should dominate synchrotron cooling after the MF decay time; and/or that the MF decays with comoving time roughly as B∝t {sup –1.5}. An internal shock synchrotron model with a decaying MF can account for the majority of GRBs with low-energy slopes not harder than ν{sup 4/3}.
79 ASTRONOMY AND ASTROPHYSICS↗
Technology to Establish a Factory for High QE Alkali Antimonide Photocathodes
Intense electron beams are key to a large number of scientific endeavors, including electron cooling of hadron beams, electron-positron colliders, secondary-particle beams such as photons and positrons, sub-picosecond ultrafast electron diffraction (UED), and new high gradient accelerators that use electron-driven plasmas. The last decade has seen a considerable interest in pursuit and realization of novel light sources such as Free Electron Lasers [1] and Energy Recovery Linacs [2] that promise to deliver unprecedented quality x-ray beams. Many applications for high-intensity electron beams have arisen in recent years in high-energy physics, nuclear physics and energy sciences, such as recent designs for an electron-hadron collider at CERN (LHeC) [3], and beam coolers for hadron beams at LHC and eRHIC [4,5]. Photoinjectors are used at the majority of high-brightness electron linacs today, due to their efficiency, timing structure flexibility and ability to produce high power, high brightness beams. The performance of light source machines is strongly related to the brightness of the electron beam used for generating the x-rays. The brightness of the electron beam itself is mainly limited by the physical processes by which electrons are generated. For laser based photoemission sources this limit is ultimately related to the properties of photocathodes [6]. Most facilities are required to expend significant manpower and money to achieve a workable, albeit often non-ideal, compromise photocathode solution. If entirely fabricated in-house, the photocathode growth process itself is laborious and not always reproducible: it involves the human element while requiring close adherence to recipes and extremely strict control of deposition parameters. Lack of growth reliability and as a consequence, slow adoption of viable photoemitter types, can be partly attributed to the absence of any centralized facility or commercial entity to routinely provide high peak current capable, low emittance, visible-light sensitive photocathodes to the myriad of source systems in use and under development. Successful adoption of photocathodes requires strict adherence to proper fabrication, operation, and maintenance methodologies, necessitating specialized knowledge and skills. Key issues include the choice of photoemitter material, development of a more streamlined growth process to minimize human operator uncertainties, accommodation of varying photoemitter substrate materials and geometries, efficient transport and insertion mechanisms preserving the photo-yield, and properly conveyed photoemitter operational and maintenance methodologies. AES, in collaboration with Cornell University in a Phase I STTR, developed an on-demand industrialized growth and centralized delivery system for high-brightness photocathodes focused upon the alkali antimonide photoemitters. To the end user, future photoemitter sourcing will become as simple as other readily available consumables, rather than a research project requiring large investments in time and personnel.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Design of a High Luminosity 100 TeV Proton Antiproton Collider
Currently new physics is being explored with the Large Hadron Collider at CERN and with Intensity Frontier programs at Fermilab and KEK. The energy scale for new physics is known to be in the multi-TeV range, signaling the need for a future collider which well surpasses this energy scale. A 10$^{\,34}$ cm$^{-2}$ s$^{-1}$ luminosity 100 TeV proton-antiproton collider is explored with 7$\times$ the energy of the LHC. The dipoles are 4.5\,T to reduce cost. A proton-antiproton collider is selected as a future machine for several reasons. The cross section for many high mass states is 10 times higher in $p\bar{p}$ than $pp$ collisions. Antiquarks for production can come directly from an antiproton rather than indirectly from gluon splitting. The higher cross sections reduce the synchrotron radiation in superconducting magnets and the number of events per bunch crossing, because lower beam currents can produce the same rare event rates. Events are also more centrally produced, allowing a more compact detector with less space between quadrupole triplets and a smaller $\beta^{*}$ for higher luminosity. To adjust to antiproton beam losses (burn rate), a Fermilab-like antiproton source would be adapted to disperse the beam into 12 different momentum channels, using electrostatic septa, to increase antiproton momentum capture 12 times. At Fermilab, antiprotons were stochastically cooled in one Debuncher and one Accumulator ring. Because the stochastic cooling time scales as the number of particles, two options of 12 independent cooling systems are presented. One electron cooling ring might follow the stochastic cooling rings for antiproton stacking. Finally antiprotons in the collider ring would be recycled during runs without leaving the collider ring, by joining them to new bunches with snap bunch coalescence and synchrotron damping. These basic ideas are explored in this work on a future 100 TeV proton-antiproton collider and the main parameters are presented.
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Multi-alkalai photocathodes production for LEReC DC gun
Low Energy RHIC electron Cooling (LEReC) is a bunched electron cooler at RHIC. The LEReC’s electron source needs provide up to 85 mA average current electron beam. The Bi-alkali photocathodes are chosen as electron source due to its long lifetime and high QE at the visible wavelength. Because the DC gun needs to produce 24/7 beams over several months, two cathode production systems and three transfer systems carrying multiple cathodes are designed and one set commissioned. In this report, we will describe our photocathode production and transfer systems and discuss the cathode's performance from cathode growth system to the DC gun.
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Particles scattering in a HVDC gun
The Electron Ion Collider (EIC) hadron cooling electron source will utilize a high average current, high voltage DC gun ,aiming to generate 1nC, 100 mA average current, and 1mm-mrad normalized emittance[1]. One of the challenges in designing and operating the HVDC gun is the occurrence of undesired "ghost" particles that disrupt the gun's operation. In other words, the high voltage power supply (HVPS) trips more frequently when pushing to higher current.
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Stochastic Cooling with Strong Band Overlap
Up to present time the stochastic cooling was only tested and used at the microwave frequencies. Majority of these stochastic cooling systems operate without Schottky band overlap which greatly simplifies tuning of cooling systems and removes unwanted coupling between different cooling systems. A transition from the microwave stochastic cooling to the optical stochastic cooling or to the coherent electron cooling increases the central frequency of cooling systems by orders of magnitude and makes impossible a cooling system operation without overlap of Schottky bands. In this paper we consider how the band overlap affects the maximum cooling rate and the optimal gain.
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Dark Matter-Electron Interactions Alter the Luminosity and Spectral Index of M87
We investigate the possibility that cosmic-ray electron cooling through dark matter-electron scatterings contributes to the low radiative efficiency observed in radio-loud galaxies such as M87. Light dark matter can scatter efficiently off electrons in M87, lowering the observed bolometric luminosity compared to astrophysical expectations. This consideration allows us to probe previously unexplored regions of the parameter space of dark matter-electron interactions. We further model the cosmic-ray electron distribution by numerically solving a diffusion equation along the jet and find that efficient dark matter-electron interactions can induce a flattening of the spectral index at different distances from the central supermassive black hole, in better alignment with radio observations from M87.
Hussein, Abdelaziz [MIT] (ORCID:0000000255608668)↗
Modeling alignment of electron trajectory in cooling section of EIC Low Energy Cooler
The Electron Ion Collider (EIC) requires cooling of protons at the injection energy to obtain emittances needed to achieve the design luminosity. The low energy cooler (LEC) provides such a capability. The LEC is an electron cooler utilizing a non-magnetized, RF-based electron cooling. This approach to cooling was successfully used in Low Energy RHIC Electron Cooler (LEReC).
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Controlled cooling of an electronic system for reduced energy consumption
Energy efficient control of a cooling system cooling an electronic system is provided. The control includes automatically determining at least one adjusted control setting for at least one adjustable cooling component of a cooling system cooling the electronic system. The automatically determining is based, at least in part, on power being consumed by the cooling system and temperature of a heat sink to which heat extracted by the cooling system is rejected. The automatically determining operates to reduce power consumption of the cooling system and/or the electronic system while ensuring that at least one targeted temperature associated with the cooling system or the electronic system is within a desired range. The automatically determining may be based, at least in part, on one or more experimentally obtained models relating the targeted temperature and power consumption of the one or more adjustable cooling components of the cooling system.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Controlled cooling of an electronic system for reduced energy consumption
Energy efficient control of a cooling system cooling an electronic system is provided. The control includes automatically determining at least one adjusted control setting for at least one adjustable cooling component of a cooling system cooling the electronic system. The automatically determining is based, at least in part, on power being consumed by the cooling system and temperature of a heat sink to which heat extracted by the cooling system is rejected. The automatically determining operates to reduce power consumption of the cooling system and/or the electronic system while ensuring that at least one targeted temperature associated with the cooling system or the electronic system is within a desired range. The automatically determining may be based, at least in part, on one or more experimentally obtained models relating the targeted temperature and power consumption of the one or more adjustable cooling components of the cooling system.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Discrepancy between electron heating and cooling rates derived from Atmosphere Explorer-C measurements
The present theory of electron temperature in the daytime mid-latitude ionosphere is tested by using Atmosphere Explorer-C measurements. In the region below 300 km, where a balance is expected between electron heating by photoelectron impact and electron cooling to ions and neutrals, we find an imbalance in which the cooling rate is consistently higher than the heating rate. The shapes of the altitude profiles also differ substantially. The cooling rate has a sharp peak at about 220 km, while the heating rate exhibits a broad peak about 30 km lower. Improved agreement is achieved at higher altitudes by using an oxygen fine structure loss rate smaller by a factor of 2, based on more recent collision strength calculations. Although this improves the overall agreement of the heating and cooling rates, the shape discrepancy remains, and the new cooling rate falls consistently below the heating rate below 200 km.
Brace, L. H.↗
Ultrafast High-Voltage Kicker System for Ion-Clearing Gaps
Ionization scattering of electron beams with residual gas molecules causes ion trapping in electron rings, both in a collider and electron cooling system. These trapped ions may cause emittance growth, tune shift, halo formation, and coherent coupled bunch instabilities. In order to clear the ions and prevent them from accumulating turn after turn, the gaps in a temporal structure of the beam are typically used. Typically, the gap in the bunch train has a length of a few percent of the ring circumference. In those regions, the extraction electrodes with high pulsed voltages are introduced. In this paper, we present the design consideration and initial test results of the high-voltage pulsed kicker hardware that includes vacuum device and pulsed voltage driver, capable of achieving over 3 kV of deflecting voltage amplitude, rise and fall times of less than 10 ns, 100 ns flat-top duration at 1.4 MHz repetition rate.
43 PARTICLE ACCELERATORS↗
MAGNETIZED ELECTRON SOURCE FOR JLEIC COOLER
Magnetized bunched-beam electron cooling is a critical part of the Jefferson Lab Electron Ion Collider (JLEIC). Strong cooling of ion beams will be accomplished inside a cooling solenoid where the ions co-propagate with an electron beam generated from a source immersed in a magnetic field. This contribution describes the production and characterization of magnetized electron beam using a compact 300 kV DC high voltage photogun and bialkali-antimonide photocathodes. Beam magnetization was studied using a diagnostic beamline that includes viewer screens for measuring the shearing angle of the electron beamlet passing through a narrow upstream slit. Correlated beam emittance with magnetic field (0-1.5 kG)at the photocathode was measured for various laser spot sizes. Measurements of photocathode lifetime were carried out at different magnetized electron beam currents up to 28 mA and high bunch charge up to 0.7 nano-Coulomb was demonstrated.
Suleiman, R.↗