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Nikhil Bachhawat

Publications and source records attributed to Nikhil Bachhawat.

5 recordsLinked to original sources
arXiv2025

CW SRF Gun generating beam parameters sufficient for CW hard-X-ray FEL

SRF CW accelerator constructed for Coherent electron Cooling (CeC) Proof-of-principle (POP) experiment at Brookhaven National Laboratory has frequently demonstrated record parameters using 1.5 nC 350 ps long electron bunches, typically compressed to FWHM of 30 ps using ballistic compression. We report experimental demonstration of CW electron beam with parameters fully satisfying requirements for hard X-ray FEL and significantly exceeding those demonstrated by APEX LCLS II electron gun. This was achieved using a 10-year-old SRF gun with a modest accelerating gradient of $\sim$15 MV/m, a bunching cavity followed by ballistic compression to generate 100 pC, $\sim$15 ps FWHM electron bunches with a normalized slice emittance of $\sim$0.2 mm-mrad and a normalized projected emittance of $\sim$0.25 mm-mrad. Hence, in this paper, we present an alternative method for generating CW electron beams for hard-X-ray FELs using existing and proven accelerator technology. We present a description of the accelerator system settings, details of projected and slice emittance measurements as well as relevant beam dynamics simulations.

physics.acc-ph↗
arXiv2025

A conservative solution to the Singularity Problem in Classical GR

We present a conservative approach to the black hole singularity problem that remains within the framework of classical General Relativity (GR) supplemented by semiclassical quantum field theory (QFT). Our construction replaces the singular interior of a black hole with a null characteristic hypersurface that carries the exterior ADM data. The excised singular interior is replaced by a conformally flat bubble manifold. We assume the characteristic data on $Σ$ are shear-quiet (vanishing Bondi news and shear to leading order) so that the initial development is conformally flat (Weyl = 0) over an early epoch. We further posit that the ingoing Hawking radiation flux provides statistically isotropic initial conditions on the bubble boundary, seeding a nearly FLRW-like epoch without first undergoing exponential inflation. The overall framework is consistent with the generalized second law of thermodynamics and offers a possible resolution of the singularity problem without invoking a full theory of quantum gravity.

gr-qc↗
arXiv2022

CERC -- Circular $e^+e^-$ Collider using Energy-Recovery Linac

We present a Circular Energy Recovery Collider (CERC) as an alternative approach for a high-energy high-luminosity electron-positron collider to current designs for high-energy electron-positron colliders either based on two storage rings with 100 km circumference or two large linear accelerators. Using Energy Recovery Linacs (ERL) located in the same-size 100 km tunnel would allow a large reduction of the beam energy losses, and therefore a reduction of the power consumption, while providing higher luminosity. It also opens a path for extending the center-of-mass (CM) energy to 500 GeV, which would enable double-Higgs production, and even to 600 GeV for production and measurements of the top Yukawa coupling. Furthermore, this approach would allow recycling of not only the energy but also of the particles. This feature opens the possibility for colliding fully polarized electron and positron beams.

physics.acc-ph↗
arXiv2019

Partial covariance two-dimensional mass spectrometry for determination of biomolecular primary structure

Mass spectrometry (MS) is used widely in biomolecular structural analysis and is particularly dominant in the study of proteins. Despite its considerable power, state-of-the-art protein MS frequently suffers from limited reliability of spectrum-to-structure assignments. This could not be solved fully by the dramatic increase in mass accuracy and resolution of modern MS instrumentation or by the introduction of new fragmentation methods. Here we present a new kind of two-dimensional mass spectrometry for high fidelity determination of a biomolecular primary structure based on partial covariance mapping. Partial covariance two-dimensional mass spectrometry (pC-2DMS) detects intrinsic statistical correlations between biomolecular fragments originating from the same or consecutive decomposition events. This enables identification of pairs of ions produced along the same fragmentation pathway of a biomolecule across its entire fragment mass spectrum. We demonstrate that the fragment-fragment correlations revealed by pC-2DMS provide much more specific information on the amino acid sequence and its covalent modifications than the individual fragment mass-to-charge ratios on which standard one-dimensional MS is based. We illustrate the power of pC-2DMS by using it to resolve structural isomers of combinatorially modified histone peptides inaccessible to standard MS.

physics.chem-ph↗