Search

At FNAL two single cell 2.6 GHz SRF cavities are being used to search for dark photons, the experiment can be conducted at 2 K or in a dilution refrigerator. Precise frequency tuning is required for these two cavities so they can be matched in frequency. A cooling capacity constraint on the dilution refrigerator only allows piezo actuators to be part of the design of the 2.6 GHz cavity tuner. The tuner is equipped with three encapsulated piezos that deliver long and short-range frequency tuning. Modifications were implemented on the first tuner design due to the low forces on the piezos caused by the cavity. Three brass rods with Belleville washers were added to the design to increase the overall force on the piezos. The testing results at 2 K are presented with the original design tuner and with the modification., 21st International Conference on Radio-Frequency Superconductivity (SRF 2023)

The PIP-II project's LB650 cavities could potentially be vulnerable to mechanical deformation because of the geometric shape of the cavity due to reduced beta. The mechanical property of the niobium half-cell was measured following various heat treatments. The 5-cell cavities were tested in a controlled drop test fashion and the real-world road test. The result showed that the 900 $\deg$C heat treatment was compatible with cavity handling and transportation during production. The test provides the bases of the transportation specification and shipping container design guidelines., Comment: 21st International Conference on Radio-Frequency Superconductivity (SRF 2023)

In dark matter searches using axion haloscopes, the search sensitivity depends on the quality factors ($Q_0$) of radiofrequency cavities immersed in multi-tesla magnetic fields. Increasing $Q_0$ would increase the scan rate through the parameter space of interest. Researchers developing superconducting radiofrequency cavities for particle accelerators have developed methods for obtaining extremely high $Q_0\sim10^{11}$ in $\mu$T-scale magnetic fields. In this paper, we describe efforts to develop high Q cavities made from Nb$_3$Sn films using a technique developed for particle accelerator cavities. Geometry optimization for this application is explored, and two cavities are tested: an existing particle accelerator-style cavity and a geometry developed and fabricated for use in high fields. A quality factor of ($5.3\pm0.3$)$\times 10^5$ is obtained at 3.9~GHz and 6~T at 4.2~K.

We present the technical and engineering design of a medium energy (10 MeV) and high average power (1 MW) electron beam accelerator intended for irradiation treatment of high volume industrial and municipal wastewater. The accelerator uses superconducting radiofrequency (SRF) cavity technology for producing the high average beam power with $>$90% RF to beam efficiency. The design of the accelerator is simplified and tailored for industrial settings by adopting the cryocooler conduction-cooling technique for the SRF cavity instead of a conventional liquid helium bath cryo-system. The technical design is supplemented with a detailed analysis of capital and operating cost of the accelerator. The designed accelerator can treat up to 12 million gallons per day of wastewater, requires capital of $\sim\$$8M for construction, and has $\sim$13.5 cents/ton/kGy in material processing cost.

This report describes a concept of an EIC cooling system, based on a proven induction linac technology with a dc electron beam. The system would operate in a full energy range of proton beams (100 - 270 GeV) and would provide 50-100 A electron beams, circulating in a cooler ring for 5 ms. Every 5 ms a new electron pulse would be injected into the cooler ring to provide continuous cooling at collisions. Operations with a 10-ms cycle is possible but it will reduce the cooling rates by ~30$\%$. The system is capable of delivering the required performance in the entire EIC energy range with emittance cooling times of less than 1-2 hours.

In Fermilab we are build and tested several superconducting Single Spoke Resonators (SSR1, \beta=0.22) which can be used for acceleration of low beta ions. Fist two cavities performed very well during cold test in Vertical Test Station at FNAL. One dressed cavity was also tested successfully in Horizontal Test Station. Currently we are building 8 cavity cryomodule for PIXIE project. Additional 10 cavities were manufactured in the industry and on-going cold test results will be presented in this poster., Comment: 3 pp. 3rd International Particle Accelerator Conference (IPAC 2012) 20-25 May 2012, New Orleans, Louisiana

Front end of a CW linac of the Project X contains an H source, an RFQ, a medium energy transport line with the beam chopper, and a SC low-beta linac that accelerates H- from 2.5 MeV to 160 MeV. SC Single Spoke Resonators (SSR) will be used in the linac, because Fermilab already successfully developed and tested a SSR for beta=0.21. Two manufactured cavities achieve 2.5 times more than design accelerating gradients. One of these cavities completely dressed, e.g. welded to helium vessel with integrated slow and fast tuners, and tested in CW regime. Successful tests of beta=0.21 SSR give us a confidence to use this type of cavity for low beta (0.117) and for high-beta (0.4) as well. Both types of these cavities are under development. In present report the basic constrains, parameters, electromagnetic and mechanical design for all the three SSR cavities, and first test results of beta=0.21 SSR are presented., Comment: 3 pp. 25th International Linear Accelerator Conference (LINAC10), 12-17 Sep 2010: Tsukuba, Japan

In the paper the Crab Cav­i­ty is de­scribed for local Crab schemes for LHC that de­mand re­duced trans­verse cav­i­ty di­men­sions small enough to fit lim­it­ed space nec­es­sary for the beams sep­a­ra­tion. The re­sults of the con­fig­u­ra­tion cav­i­ty op­ti­miza­tion are pre­sent­ed that in­clude (a) the sur­face field min­i­miza­tion; (b) par­a­sitic monopole and dipole spec­trum op­ti­miza­tion and dump­ing, (c) the input and the par­a­sitic mode damp­ing cou­plers de­sign. The re­sults of mul­ti­pact­ing sim­u­la­tions, which were per­formed in order to un­der­stand the pos­si­ble gra­di­ent lim­i­ta­tions, are dis­cussed also.

TESLA Reports 2003 14 pp. (2003).

The 7th European Particle Accelerator Conference EPAC 2000, EPAC 2000, Vienna, Austria, 26 Jun 2000 - 30 Jun 2000; Hamburg : DESY 327-329 (2000)., Since several years the development of seamless niobium cavity fabrication by hydro forming is being pursued at DESY. This technique offers the possibility of lower cost of fabrication and perhaps better rfperformance of the cavities because of the elimination of electron-beam welds, which in the standard fabrication technique have sometimes lead to inferior cavity performance due to defects. Several single cell 1300 MHz cavities have been formed from high purity seamless niobium tubes, which are under computer control expanded with internal pressure while simultaneously being swaged axially. The seamless tubes have been made by either back extrusion and flow forming or by spinning or deep drawing. Standard surface treatment techniques such as high temperature post purification, buffered chemical polishing(BCP), electropolishing (EP) and high pressure ultra pure water rinsing (HPR) have been applied to these cavities. The cavities exhibited high Q - values of 2 x 10$^10$ at 2K and residual resistances as low as 3 n$\Omega$ after the removal of a surface layer of app. 100 $\mu$m by BCP. Surprisingly, even at high gradients up to the maximum measured values of E$_{acc}$ $\approx$ 33 MV/m the Q-value did not decrease in the absence of field emission as often observed. After electropolishing of additional 100 $\mu$m one of the cavities reached an accelerating gradient of E$_{acc}$ $\geq$ 42 MV/m., Published by DESY, Hamburg

TESLA Reports 78 pp. (1999).