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Mokhov, N.

Publications and source records attributed to Mokhov, N..

16 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Feasibility of crystal-assisted collimation in the CERN accelerator complex

Bent silicon crystals mounted on high-accuracy angular actuators were installed in the CERN Super Proton Synchrotron (SPS) and extensively tested to assess the feasibility of crystal-assisted collimation in circular hadron colliders. The adopted layout was exploited and regularly upgraded for about a decade by the UA9 Collaboration. The investigations provided the compelling evidence of a strong reduction of beam losses induced by nuclear inelastic interactions in the aligned crystals in comparison with amorphous orientation. A conceptually similar device, installed in the betatron cleaning insertion of CERN Large Hadron Collider (LHC), was operated through the complete acceleration and storage cycle and demonstrated a large reduction of the background leaking from the collimation region and radiated into the cold sections of the accelerator and the experimental detectors. The implemented layout and the relevant results of the beam tests performed in the SPS and in the LHC with stored proton and ion beams are extensively discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Promising Technologies and R&D Directions for the Future Muon Collider Detectors

Among the post-LHC generation of particle accelerators, the muon collider represents a unique machine with capability to provide very high energy leptonic collisions and to open the path to a vast and mostly unexplored physics programme. However, on the experimental side, such great physics potential is accompanied by unprecedented technological challenges, due to the fact that muons are unstable particles. Their decay products interact with the machine elements and produce an intense flux of background particles that eventually reach the detector and may degrade its performance. In this paper, we present technologies that have a potential to match the challenging specifications of a muon collider detector and outline a path forward for the future R&D efforts.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Low-temperature proton irradiation damage of isotropic nuclear grade IG-430 graphite

IG-430, a fine-grained, isotropic graphite grade is a promising candidate for the future Very High Temperature Reactors (VHTR). IG-430 which provides higher density, strength, and thermal conductivity, has already been developed as a graphite for next-generation HTGR, and is expected to be employed. This graphite grade, however, is lacking enough database that is needed for design. The present study aims to enhance the database with experimental data focusing on the low temperature regime (90–210 °C) by using 120–200 MeV protons to irradiate the IG-430 graphite to peak fluence of ~1.2 10 25 m –2 . It is anticipated that radiation-induced changes in the graphite properties and damage to be more pronounced in this low temperature regime than in elevated temperatures where damage annealing is taking place simultaneously. IG-430 graphite was characterized following irradiation for mechanical property changes (modulus and strength), dimensional stability and irradiation-induced growth as well as microstructural changes using high energy X-rays and different X-ray diffraction techniques. In assessing proton irradiation effects on the IG-430 graphite grade, comparison of radiation effects was made with the IG-43 grade, the un-purified version of IG-430, as well as other isotropic graphite grades. IG-430 was shown in this study to be better graphitized than other isotropic graphite grades. The study also revealed that during proton irradiation at low temperatures (~100 °C) the IG-430 exhibits stored energy release.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Expression of Interest: Rare Eta Decays with a TPC for Optical Photons

The REDTOP experiment is primarily intended to look for new violations of basic symmetry principles and conservation laws in particle physics. Our main focus will be on very rare decays of the η meson. From the Standard Model and other theories, such decays can provide distinct insights into the limits of conservation laws and open unique doors to new ones at branching ratio sensitivity levels typically below 10 -9 . Notably, current experimental upper limits for η decays are many orders of magnitude larger. The sensitivity goal of our experiment is expected to be better than 10 -10 for most decay modes, based on an estimated yield of more than 10 12 η mesons per year. Numerous opportunities for new physics Beyond the Standard Model will become available.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Final report: Conceptual design of a 10-megawatt electron beam irradiation facility for bio-solid waste treatment

In this report, a conceptual design is proposed for a 10 mega-watt (MW) electron beam accelerator for wastewater treatment. This is done by applying the latest accelerator technologies developed at Fermilab and within the Department of Energy (DOE) Office of Science laboratory complex. This report expands on previous work on the 1 MW accelerator, which was developed with requirements from Metropolitan Water Reclamation District (MWRD) in Chicago. The full report of the previous effort is available from the Office of High Energy Physics Accelerator Stewardship Program [1].

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

νSTORM - Neutrinos from STORed Muons: Letter of Intent to the Fermilab Physics Advisory Committee

The idea of using a muon storage ring to produce a high-energy (≃ 50 GeV) neutrino beam for experiments was first discussed by Koshkarev in 1974. A detailed description of a muon storage ring for neutrino oscillation experiments was first produced by Neuffer in 1980. In his paper, Neuffer studied muon decay rings with E μ of 8, 4.5 and 1.5 GeV. With his 4.5 GeV ring design, he achieved a figure of merit of ≃ 6 x 10 9 useful neutrinos per 3 x 10 13 protons on target. The facility we describe here (νSTORM) is essentially the same facility proposed in 1980 and would utilize a 3-4 GeV/c muon storage ring to study eV-scale oscillation physics and, in addition, could add significantly to our understanding of ν e and ν μ cross sections. In particular the facility can: (1) address the large Δm 2 oscillation regime and make a major contribution to the study of sterile neutrinos, (2) make precision ν e and $\bar{ν}$ e cross-section measurements, (3) provide a technology (μ decay ring) test demonstration and μ beam diagnostics test bed, and (4) provide a precisely understood ν beam for detector studies. The facility is the simplest implementation of the Neutrino Factory concept. In our case, 60 GeV/c protons are used to produce pions off a conventional solid target. The pions are collected with a focusing device (horn or lithium lens) and are then transported to, and injected into, a storage ring. The pions that decay in the first straight of the ring can yield a muon that is captured in the ring. The circulating muons then subsequently decay into electrons and neutrinos. We are starting with a storage ring design that is optimized for 3.8 GeV/c muon momentum. This momentum was selected to maximize the physics reach for both oscillation and the cross section physics. See Fig. 1 for a schematic of the facility.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Demagnetization of Nd 2 Fe 14 B, Pr 2 Fe 14 B, and Sm 2 Co 17 Permanent Magnets in Spallation Irradiation Fields

Prompted by the need for radiation-resistant permanent magnets for insertion devices (IDs) of high-brilliance next-generation synchrotrons such as the National Synchrotron Light Source II, the demagnetization of Nd 2 Fe 14 B and Pr 2 Fe 14 B was studied after exposure to a mixed irradiating field. Degradation and damage of the permanent magnetic material by components of electromagnetic showers induced in magnets by intense high-energy electron beams will alter the magnetic field structure of the IDs. Plate-like Nd 2 Fe 14 B magnets were irradiated to 1.8 Grad dose and were evaluated against Pr 2 Fe 14 B magnets irradiated to a lower dose of 20 Mrad. In addition, annular Sm 2 Co 17 and Nd 2 Fe 14 B magnets integrated within a ferrofluidic feedthrough (FFFT) rotary seal were also irradiated to dose levels of 2 Grad for Sm 2 Co 17 and 20 Mrad for Nd 2 Fe 14 B. Post-irradiation measurements of the magnetic intensity revealed that severe demagnetization exceeding 85% occurs in Nd 2 Fe 14 B magnets after only 50 Mrad dose and over 87% for Pr 2 Fe 14 B after 10 Mrad dose. The annular-shaped Sm 2 Co 17 magnets of the FFFTs were almost insensitive to irradiation up to a dose of 2 Grad. Annular-shaped Nd 2 Fe 14 B magnets also showed resistance to demagnetization, a direct consequence of the annular shape which is characterized by the removal of the stronger demagnetizing field present at the center of a disk-like magnet. As a result, the sensitivity of boron-based permanent magnets to neutron energy (thermal versus fast) was also assessed via specifically designed experiments and discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

The MARS15-based FermiCORD code system for calculation of the accelerator-induced residual dose

The FermiCORD code system, a set of codes based on MARS15 that calculates the accelerator-induced residual doses at experimental facilities of arbitrary configurations, has been developed. FermiCORD is written in C++ as an add-on to Fortran-based MARS15. The FermiCORD algorithm consists of two stages: 1) simulation of residual doses on contact with the surfaces surrounding the studied location and of radionuclide inventories in the structures surrounding those locations using MARS15, and 2) simulation of the emission of the nuclear decay gamma-quanta by the residuals in the activated structures and scoring the prompt doses of these gamma-quanta at arbitrary distances from those structures. The FermiCORD code system has been benchmarked against similar algorithms based on other code systems and showed a good agreement. In conclusion, the code system has been applied for calculation of the residual dose of the target station for the Mu2e experiment and the results have been compared to approximate dosimetric approaches.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Proton irradiated graphite grades for a long baseline neutrino facility experiment

In search of a low-Z pion production target for the Long Baseline Neutrino Facility (LBNF) of the Deep Underground Neutrino Experiment (DUNE) four graphite grades were irradiated with protons in the energy range of 140–180 MeV, to peak fluence of ~6.1×10 20 p/cm 2 and irradiation temperatures between 120–200 °C. The test array included POCO ZXF-5Q, Toyo-Tanso IG 430, Carbone-Lorraine 2020 and SGL R7650 grades of graphite. Irradiation was performed at the Brookhaven Linear Isotope Producer. Postirradiation analyses were performed with the objective of (a) comparing their response under the postulated irradiation conditions to guide a graphite grade selection for use as a pion target and (b) understanding changes in physical and mechanical properties as well as microstructure that occurred as a result of the achieved fluence and in particular at this low-temperature regime where pion graphite targets are expected to operate. A further goal of the postirradiation evaluation was to establish a proton-neutron correlation damage on graphite that will allow for the use of a wealth of available neutron-based damage data in proton-based studies and applications. Macroscopic postirradiation analyses as well as energy dispersive x-ray diffraction of 200 KeV x rays at the NSLS synchrotron of Brookhaven National Laboratory were employed. The macroscopic analyses revealed differences in the physical and strength properties of the four grades with behavior however under proton irradiation that qualitatively agrees with that reported for graphite under neutrons for the same low temperature regime and in particular the increase of thermal expansion, strength and Young’s modulus. The proton fluence level of ~10 20 cm -2 where strength reaches a maximum before it begins to decrease at higher fluences has been identified and it agrees with neutron-induced changes. X-ray diffraction analyses of the proton irradiated graphite revealed for the first time the similarity in microstructural graphite behavior to that under neutron irradiation and the agreement between the fluence threshold of ~5×10 20 cm -2 where the graphite lattice undergoes a dramatic change. The confirmed similarity in behavior and agreement in threshold fluences for proton and neutron irradiation effects on graphite reported for the first time in this study will enable the safe utilization of the wealth of neutron irradiation data on graphite that extends to much higher fluences and different temperature regimes by the proton accelerator community searching for multi-MW graphite targets.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

A STUDY OF THE ENERGY DEPENDENCE OF RADIATION DAMAGE IN SUPERCONDUCTING COILS FOR A NEXT GENERATION MU2E AT PIP - II

The Mu2e experiment at Fermilab is being designed to study the coherent neutrino-less conversion of a negative muon into an electron in the field of a nucleus. This process has an extremely low probability in the Standard Model, and its observation would provide unambiguous evidence for beyond the standard model physics. The Mu2e design aims to reach a single-event-sensitivity of about 2.5 x $10^{-17}$ and will probe effective new physics mass scales in the $10^{3}-10^{4}$ TeV range, well beyond the reach of the LHC. This work will examine the maximum beam power that can be tolerated for beam energies in the 0.5-8 GeV range. This has implications for how the sensitivity might be further improved with a second generation experiment using an upgraded proton beam from the PIP-II project, which will be capable of providing MW beams to Fermilab experiments later in the next decade.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Measurements of production cross sections of 10Be and 26Al by 120GeV and 392MeV proton bombardment of 89Y, 159Tb, and natCu targets

The production cross sections of 10 Be and 26 Al were measured by accelerator mass spectrometry using 89 Y, 159 Tb, and nat Cu targets bombarded by protons with energies Ep of 120GeV and 392MeV. The production cross sections obtained for 10 Be and 26 Al were compared with those previously reported using Ep=50MeV–24GeV and various targets. It was found that the production cross sections of 10 Be monotonically increased with increasing target mass number when the proton energy was greater than a few GeV. On the other hand, it was also found that the production cross sections of 10 Be decreased as the target mass number increased from that of carbon to those near the mass numbers of nickel and zinc when the proton energy was below approximately 1GeV. They also increased as the target mass number increased from near those of nickel and zinc to that of bismuth, in the same proton energy range. Similar results were observed in the production cross sections of 26 Al, though the absolute values were quite different between 10 Be and 26 Al. The difference between these production cross sections may depend on the impact parameter (nuclear radius) and/or the target nucleus stiffness.

120 GeV proton↗
DOE OSTI2014

Small angle detectors for study diffractive processes with CMS

The approach and detectors for diffractive physics based on two current projects—Forward Shower Counter (FSC) and Proton Precision Spectrometer (PPS) are presented. FSC system consists of six (3+3) Stations of scintillator counters, which surround closely the beam pipes along 59 m < |z| < 140 m from IP5 on both plus (+) and minus (-) sides. These will detect showers from very forward particles with rapidity 7.5 < |η| < 10 interacting in the beam pipe and surrounding material. FSC allow measurements of single diffraction: p+p → p+G+X (where G is rapidity gap) for lower masses and double diffraction p+p → X+G+X with a large central rapidity gap. The counters can also be used for beam real-time monitoring and will make an invaluable contribution to the understanding of the background environment and its topology. PPS is designed for study the central exclusive production pp → p+X+p, where the + signs denote the absence of hadronic activity (that is, the presence of a rapidity gap) between the outgoing protons and the decay products of the central system X. The precise measurement of the kinematical parameters of the outgoing protons enables to study the properties of the central state X. In PPS part we consider the detector for high precision timing of these protons—QUARTIC. It consists of L-shape bars with quartz or sapphire radiator. The time resolution of the QUARTIC prototypes achieved ≈ 10 ps.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗