arXiv subjects

A. Pathak

Publications and source records attributed to A. Pathak.

10 recordsLinked to original sources

arXiv2025

Optics Reconstruction in the SCL Section of the FNAL Linac

The Side-Coupled Linac (SCL) section of the FNAL linac accelerates the beam from 117 MeV to 401.5 MeV, operating at 22-24 mA beam current. Transverse focusing is performed by 32 quadrupoles, and the beam orbit is guided by 19 dipole correctors and measured by 29 BPMs. The bunch length is measured in a single location by a Bunch Shape Monitor (BSM). This paper presents a three-step reconstruction of the machine optics. First, the transverse and longitudinal Twiss parameters at the start of the SCL section are determined using quadrupole scans and BSM measurements at different settings of an upstream cavity. Second, the quadrupole calibrations are adjusted based on differential-trajectory measurements. Finally, the beam is propagated along the SCL linac using the code TraceWin. A comparison between TraceWin simulations and the beam envelope measured by the 12 wire scanners of the SCL linac was performed. Transverse and longitudinal beam parameters at the entrance of the transition section will be reported.

physics.acc-ph↗

arXiv2025

Measuring Orbit Responses with Oscillating Trajectories in the Fermilab Linac

Recording changes in beam transverse positions re-ported by Beam Position Monitors (BPMs) in response to a beam deflection by an upstream dipole corrector (orbit response) is a powerful tool for analysis of accelerator optics and assisting with machine tuning. In the Fermilab Linac, orbit responses are recorded by oscillating the currents of up to 19 correctors, providing faster, drift-resistant measurements through frequency-domain analysis. This report describes the technique, including error estimations and consistency checks and shows an example of the measurements.

physics.acc-ph↗

arXiv2025

Design and Commissioning of Readout Electronics for a $K_L^0$ and $\mu$ Detector at the Belle II Experiment

The K-long and muon detector (KLM) constitutes the outer-most volume of the Belle II spectrometer at the interaction region of the SuperKEKB collider in Tsukuba, Japan. The KLM detector was partially upgraded since the Belle experiment by replacing many of its resistive-plate chambers with scintillators containing wavelength-shifting fibers and instrumenting it with silicon photomultipliers. We describe the readout electronics, firmware, and software created to control and acquire data from the scintillators and resistive-plate chambers.

hep-ex↗

arXiv2024

Space charge dominated momentum spread and compensation strategies in the post-linac section of Proton Improvement Plan-II at Fermilab

The upcoming Proton Improvement Plan-II (PIP-II), designated for enhancements to the Fermilab accelerator complex, features a new 800 MeV superconducting linac and a Beam Transfer Line (BTL) to transport the beam to the existing Booster synchrotron. To mitigate the space charge tune shift associated with a high intensity accumulated beam, the low emittance linac beam is used to paint the ring phase space both transversely and longitudinally. To prevent losses caused by particles injected outside the rf separatrix while painting longitudinal phase space, the momentum spread of the incoming beam should not exceed 2.1 x 10^-4. Detailed simulations showed that due to space charge, the rms momentum spread increases to 4 x 10^-4 while it is transported in the BTL --about twice the allowable limit. In this paper, we outline a mitigation strategy involving a debuncher cavity. We discuss location, operating frequency, and gap voltage under both nominal and perturbed beam conditions, specifically accounting for momentum jitter. The impact of cavity misalignments is also assessed. The paper concludes by recommending an optimized configuration.

physics.acc-ph↗

arXiv2015

Relationship between X-ray spectral index and X-ray Eddington ratio for Mrk 335 and Ark 564

We present a comprehensive flux resolved spectral analysis of the bright Narrow line Seyfert I AGNs, Mrk~335 and Ark~564 using observations by XMM-Newton satellite. The mean and the flux resolved spectra are fitted by an empirical model consisting of two Comptonization components, one for the low energy soft excess and the other for the high energy power-law. A broad Iron line and a couple of low energies edges are required to explain the spectra. For Mrk~335, the 0.3 - 10 keV luminosity relative to the Eddington value, L{$_{X}$}/L$_{Edd}$, varied from 0.002 to 0.06. The index variation can be empirically described as $\Gamma$ = 0.6 log$_{10}$ L{$_{X}$}/L$_{Edd}$ + 3.0 for $0.005 < L{_{X}}/L_{Edd} < 0.04$. At $ L_{{X}}/L_{Edd} \sim 0.04$ the spectral index changes and then continues to follow $\Gamma$ = 0.6 log$_{10}$ L$_{{X}}$/L$_{Edd}$ + 2.7, i.e. on a parallel track. We confirm that the result is independent of the specific spectral model used by fitting the data in the 3 - 10 keV band by only a power-law and an Iron line. For Ark~564, the index variation can be empirically described as $\Gamma$ = 0.2 log$_{10}$ L$_{{X}}$/L$_{Edd}$ + 2.7 with a significantly large scatter as compared to Mrk~335. Our results indicate that for Mrk~335, there may be accretion disk geometry changes which lead to different parallel tracks. These changes could be related to structural changes in the corona or enhanced reflection at high flux levels. There does not seem to be any homogeneous or universal relationship for the X-ray index and luminosity for different AGNs or even for the same AGN.

astro-ph.GA↗

arXiv2010

Survey of O VI absorption in the Large Magellanic Cloud

We present a survey of interstellar O VI absorption in the Large Magellanic Cloud (LMC) towards 70 lines of sight based on Far Ultraviolet Spectroscopic Explorer (FUSE) observations. The survey covers O VI absorption in a large number of objects in different environmental conditions of the LMC. Overall, a high abundance of O VI is present in active and inactive regions of the LMC with mean log[N(O VI)] = 14.23 atoms cm$^{-2}$. There is no correlation observed between O VI absorption and emissions from the hot gas (X-ray surface brightness) or the warm gas (H$_{\alpha}$ surface brightness). O VI absorption in the LMC is patchy and the properties are similar to that of the Milky Way (MW). In comparison to the Small Magellanic Cloud (SMC), O VI is lower in abundance even though SMC has a lower metallicity compared to the LMC and the MW. We present observations in 10 superbubbles of the LMC of which we detect O VI absorption in 5 superbubbles for the first time and the superbubbles show an excess O VI absorption of about 40% compared to non-superbubble lines of sight. We have also studied the properties of O VI absorption in the 30 Doradus region. Even though O VI does not show any correlation with X-ray emission for the LMC, a good correlation between log[N(O VI)] and X-ray surface brightness for 30 Doradus region is present. We also find that O VI abundance decreases with increasing distance from the star cluster R136.

astro-ph.GA↗

arXiv2005

Non-destructive Orthonormal State Discrimination

We provide explicit quantum circuits for the non-destructive deterministic discrimination of Bell states in the Hilbert space $C^{d^{n}}$, where $d$ is qudit dimension. We discuss a method for generalizing this to non-destructive measurements on any set of orthogonal states distributed among $n$ parties. From the practical viewpoint, we show that such non-destructive measurements can help lower quantum communication complexity under certain conditions.

quant-ph↗

arXiv2005

Modified Grover's search algorithm for the cases where the number of solutions is known

Grover's search algorithm searches a database of $N$ unsorted items in $O(\sqrt{N/M})$ steps where $M$ represents the number of solutions to the search problem. This paper proposes a scheme for searching a database of $N$ unsorted items in $O(logN)$ steps, provided the value of $M$ is known. It is also shown that when $M$ is unknown but if we can estimate an upper bound of possible values of $M$, then an improvement in the time complexity of conventional Grover's algorithm is possible. In that case, the present scheme reduces the time complexity to $O(MlogN)$.

quant-ph↗

arXiv2005

Modified Grover's Search Algorithm in O(M+logN)Steps

The present letter proposes a modification in the well known Grover's search algorithm, which searches a database of $N$ unsorted items in $O(\sqrt{N/M})$ steps, where $M$ represents the number of solutions to the search problem. Concurrency control techniques and extra registers for marking and storing the solutions are used in the modified algorithm. This requires additional space but it is shown that the use of extra register and marking techniques can reduce the time complexity to $O(M+\log N)$.

quant-ph↗

arXiv2005

Quantum Floyd-Warshall Alorithm

Classical Floyd-Warshall algorithm is used to solve all-pairs shortest path problem on a directed graph. The classical algorithm runs in \mathcal{O} (V^{3}) time where V represents the number of nodes. Here we have modified the algorithm and proposed a quantum algorithm analogous to Floyd-Warshall algorithm which exploits the superposition principle and runs in \mathcal{O} (Vlog_{2}V) time.

quant-ph↗