dorsal/arxiv
View SchemaAnalysis of Thermally Induced Frequency Shift for the Spallation Neutron Source RFQ
| Authors | S. Virostek, J. Staples |
|---|---|
| Categories | |
| ArXiv ID | physics/0008169 |
| URL | https://arxiv.org/abs/physics/0008169 |
| Journal | eConf C000821 (2000) THD04 |
Abstract
The Spallation Neutron Source (SNS) Front-End Systems Group at Lawrence Berkeley National Lab (LBNL) is developing a Radio Frequency Quadrupole (RFQ) to accelerate an H- beam from 65 keV to 2.5 MeV at the operating frequency of 402.5 MHz. The 4 section, 3.7 meter long RFQ is a 4 vane structure operating at 6% duty factor. The cavity walls are made from OFE Copper with a GlidCop outer layer to add mechanical strength. A set of 12 cooling channels in the RFQ cavity walls are fed and controlled separately from 4 channels embedded in the vanes. An ANSYS finite-element model has been developed to calculate the deformed shape of the cavity for given RF heat loads and cooling water temperatures. By combining the FEA results with a SUPERFISH RF cavity simulation, the relative shift in frequency for a given change in coolant temperature or heat load can be predicted. The calculated cavity frequency sensitivity is -33 kHz per 1 degC change in vane water temperature with constant-temperature wall water. The system start-up transient was also studied using the previously mentioned FEA model. By controlling the RF power ramp rate and the independent wall and vane cooling circuit temperatures, the system turn-on time can be minimized while limiting the frequency shift.
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"abstract": "The Spallation Neutron Source (SNS) Front-End Systems Group at Lawrence\nBerkeley National Lab (LBNL) is developing a Radio Frequency Quadrupole (RFQ)\nto accelerate an H- beam from 65 keV to 2.5 MeV at the operating frequency of\n402.5 MHz. The 4 section, 3.7 meter long RFQ is a 4 vane structure operating at\n6% duty factor. The cavity walls are made from OFE Copper with a GlidCop outer\nlayer to add mechanical strength. A set of 12 cooling channels in the RFQ\ncavity walls are fed and controlled separately from 4 channels embedded in the\nvanes. An ANSYS finite-element model has been developed to calculate the\ndeformed shape of the cavity for given RF heat loads and cooling water\ntemperatures. By combining the FEA results with a SUPERFISH RF cavity\nsimulation, the relative shift in frequency for a given change in coolant\ntemperature or heat load can be predicted. The calculated cavity frequency\nsensitivity is -33 kHz per 1 degC change in vane water temperature with\nconstant-temperature wall water. The system start-up transient was also studied\nusing the previously mentioned FEA model. By controlling the RF power ramp rate\nand the independent wall and vane cooling circuit temperatures, the system\nturn-on time can be minimized while limiting the frequency shift.",
"arxiv_id": "physics/0008169",
"authors": [
"S. Virostek",
"J. Staples"
],
"categories": [
"physics.acc-ph"
],
"journal_ref": "eConf C000821 (2000) THD04",
"title": "Analysis of Thermally Induced Frequency Shift for the Spallation Neutron Source RFQ",
"url": "https://arxiv.org/abs/physics/0008169"
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