arXiv subjects

J. Subedi

Publications and source records attributed to J. Subedi.

6 recordsLinked to original sources

arXiv2026

Heat load measurements for the PIP-II pHB650 cryomodule

Phase-3 testing of the pHB650 cryomodule at the PIP-II Injector Test Facility was conducted to evaluate the effectiveness of heat load mitigations performed after earlier phases of testing and to continue pinpointing any sources of unexpectedly high heat loads.. The programme measured HTTS, LTTS, and 2 K isothermal/non-isothermal loads under "standard", "linac", and "simulated dynamic" operating modes, recording data both inside the cryomodule and across the bayonet can circuits. Thermal-acoustic oscillations were eliminated by replacing the original G10 cooldown-valve stem with a stainless-steel stem fitted with wipers. A newly developed Python script automated acquisition of ACNET data, performed real-time heat-load calculations, and generated plots and tables that were posted to the electronic logbook within minutes, vastly reducing manual effort and accelerating feedback between SRF and cryogenics teams. Analysis showed that JT heat-exchanger effectiveness and temperature stratification in the two-phase and relief piping strongly influence the observed loads and helped isolate sources of excess heat. The campaign demonstrates that rigorous pre-test planning, real-time diagnostics, and automated reporting can improve both accuracy and efficiency, providing a template for future PIP-II cryomodule tests and for implementing targeted heat-load mitigations.

physics.acc-ph↗

arXiv2025

Integration and commissioning plan of Full Flow Purifier at Muon Campus

The Full Flow Purifier for Fermilab's Muon Campus uses a charcoal bed surrounded by a liquid nitrogen jacket to purify up to 240 g/s of helium gas. Fabrication by Ability Engineering Technology Inc. has been completed and the purifier delivered to Fermilab. It is the largest purifier to be used at Fermilab based on both capacity and size. A previous paper discussed the design of purifier for various operational conditions and horizontal shipping. The purifier is designed to withstand 5g force in vertical and 2g force in lateral and longitudinal directions. Transportation experience from vendor to Fermilab and within site is discussed. Integration of the purifier involved design and fabrication of a liquid nitrogen transfer line, regeneration system, and helium piping to connect it to Muon Campus cryogenic system. It also involved establishing electrical, instrumentation and controls connections to the system. Integration of the purifier is discussed in detail. The purifier is to be commissioned using up to 4 MYCOM helium compressors to supply helium and liquid nitrogen supplied by a 60,000-liter tank. Actual effectiveness of the 3-stream heat exchanger is to be estimated based on measured temperatures and flow rate. Impurity levels will be monitored at inlet and outlet of the purifier. Theoretical adsorption capacity of the purifier is calculated based on the measured temperatures and flowrates and is compared to actual adsorption capacity over time.

physics.acc-ph↗

arXiv2024

Cold Test Results of Pre-Production PIP-II SSR2 Cavities with High-Power Couplers in the Fermilab Spoke Test Cryostat

As part of the PIP-II project at Fermilab, a pre-production cryomodule featuring 325 MHz Single Spoke Resonator type 2 (SSR2) superconducting RF cavities is under construction. These SSR2 cavities are fabricated by industry partners and undergo initial cold testing at our collaborating institution, IJCLab in France, utilizing low-power coupler. Subsequently, the cavities are subjected to final qualification at Fermilab, complete with tuner and high-power coupler assemblies. This paper provides an overview of the ongoing efforts dedicated to high-power testing of jacketed SSR2 cavities in the Spoke Test Cryostat (STC) at Fermilab. Performance parameters obtained from these tests are presented, offering valuable insights into the cavities operational characteristics and readiness for integration into the PIP-II cryomodule.

physics.acc-ph↗

arXiv2024

Performance of PIP-II High-beta 650 Cryomodule After Transatlantic Shipping

After shipment to the Daresbury Lab and return to Fermilab, the prototype HB650 cryomodule underwent another phase of 2K RF testing to ascertain any performance issues that may have arisen from the transport of the cryomodule. While measurements taken at room temperature after the conclusion of shipment indicated that there were no negative impacts on cavity alignment, beamline vacuum, or cavity frequency, testing at 2K was required to validate other aspects such as tuner operation, cavity coupling, cryogenic system integrity, and cavity performance. Results of this latest round of limited 2K testing will be presented.

physics.acc-ph↗

arXiv2023

Nitrogen Precooling Heat Exchanger replacement and control system upgrade in Superfluid Cryoplant at CMTF

Liquid Nitrogen precooling is used in most Cryoplants to achieve cooldown to 80 K temperature range. In one such system at Fermilab's CMTF Superfluid Cryoplant, where the Helium supply directly exchanges heat with liquid Nitrogen, freezing of Nitrogen occurred inside the heat exchanger due to heat exchanger imbalance during a Cryoplant trip. Trapped vapor pockets of N2 within the frozen heat exchanger channels were formed while warming up the heat exchanger, creating high localized pressure and subsequent damage/rupture of the heat exchanger. Replacement of the heat exchanger was done, and modifications were made in the system to rectify future occurrences. The control system was updated to bypass the heat exchanger entirely if the incoming Helium stream temperature drops below 76 K. This was done by repurposing two control valves as heat exchanger bypass valves that were previously used for a redundant 80 K adsorber in the coldbox. Additional modifications were made to further prevent return of large amount of cold Helium gas from cold end during abrupt Cryoplant shutdown. This modification has ensured high reliability of heat exchanger with prevention of freezing of Nitrogen which can damage the heat exchanger.

physics.ins-det↗

arXiv2023

Design of Muon Campus full flow purifier for varying operational conditions and horizontal shipping

Constant ingress of impurities in Muon Campus g-2 experiment at Fermilab has resulted in reduction of efficiency of cryogenic expanders and occasional undesired downtime to flush the impurities. Due to insufficiency of current 60 g/s mobile purifier, a full flow purifier is designed to be used in Muon Campus which purifies 240 g/s of Helium throughput of 4 compressors through charcoal bed at 80 K and returns ambient Helium back to the system. The purifier is designed to be operated near liquid Nitrogen temperature during cold operations and up to 400 K during regeneration. Both warm and cold operational range of the purifier has required use of appropriate clearances in design due to expansion and contraction. The vessel of around 16 ft height which is designed to be operated vertically is to be shipped horizontally. The asymmetrical position of heavy stainless steel heat exchanger in the purifier support frame and 5g vertical load design consideration for shipping has required use of shipping supports and heat exchanger rotational stops to comply with design requirements. FEA of purifier system is performed in cold, warm and shipping cases to verify that the purifier satisfies the design requirements.

physics.ins-det↗