Vibration Analysis of a Cryocooler for CDMS Lauren Coutant SULI, summer 2007

What is CDMS? Cryogenic Dark Matter Search (CDMS) Cryogenic Dark Matter Search (CDMS) It is known that dark matter exists [1] It is known that dark matter exists [1] Best theory: it is Weakly Interacting Massive Particles (WIMPs) [2] Best theory: it is Weakly Interacting Massive Particles (WIMPs) [2] CDMS is a direct detection experiment CDMS is a direct detection experiment Detects the energy transferred when a WIMP has a collision with a nucleus in the detector Detects the energy transferred when a WIMP has a collision with a nucleus in the detector Detector is kept at 50mK with a Gifford McMahon cryocooler and dilution refrigerator Detector is kept at 50mK with a Gifford McMahon cryocooler and dilution refrigerator

Two Types of Cryocoolers Gifford-McMahon (GM) Gifford-McMahon (GM) Uses a piston to push the working fluid through the system Uses a piston to push the working fluid through the system Piston is located in the cryocooler Piston is located in the cryocooler Pulse Tube (PT) Pulse Tube (PT) Uses orifice and reservoir instead of piston Uses orifice and reservoir instead of piston Has no moving mechanical parts inside the cryocooler [3] Has no moving mechanical parts inside the cryocooler [3] [4]

Stirling (GM) versus PT Cycle [5] StirlingPulse Tube

Potential Problems from Cryocooler All Cryocoolers have some vibration All Cryocoolers have some vibration Vibration can cause Vibration can cause Heat Heat Electrical noise, ~T 5 Electrical noise, ~T 5 “Vibration free” “Vibration free” Vibration on the order of background seismic motion [6] Vibration on the order of background seismic motion [6]

What Causes the Vibrations? GM GM Piston causes motion in the system Piston causes motion in the system PT PT Fluid traveling through impedances—think of musical instruments Fluid traveling through impedances—think of musical instruments Both Both Pressure changes of the working fluid cause pipes to deform—think of blood vessels Pressure changes of the working fluid cause pipes to deform—think of blood vessels [7]

Which one is better? [8] p. 314

What type was tested here? Cryomech Pulse Tube 415 Cryomech Pulse Tube 415 Two Stage Two Stage 1 st Stage of the Cryocooler--room temperature to 77K 1 st Stage of the Cryocooler--room temperature to 77K 2 nd Stage--77K to 4K 2 nd Stage--77K to 4K [9]

Vibration Analysis

Accelerometer Piezoelectric material experiences charge separation when a force is applied Piezoelectric material experiences charge separation when a force is applied Voltage can be measured and related to the magnitude of the force Voltage can be measured and related to the magnitude of the force Force can be used to find acceleration, F=ma Force can be used to find acceleration, F=ma Adapted from [10]

Vibration Testing: Accelerometer Location

Vibration Testing: Block Diagram

Vibration Analysis: Lab 3 Set up

Results As a reference, g=9.8 m/s^2

Comparison How does this relate to what Tomaru’s group got? How does this relate to what Tomaru’s group got? How does this relate to the performance of the current CDMS cryocooler? How does this relate to the performance of the current CDMS cryocooler?

Vibration Reduction Methods Distance Distance Cold head placed away from cryocooler [3] Cold head placed away from cryocooler [3] Was implemented in Lab 3 Was implemented in Lab 3 Flexible material to absorb vibrations Flexible material to absorb vibrations Rigid material to resist elastic deformation Rigid material to resist elastic deformation Active vibration cancellation Active vibration cancellation

Vibration Reduction Methods: Materials and Counter-weight Adapted from [11] p. 118

Vibration Reduction Methods: Distance and Materials [8] p. 310

Vibration Reduction Methods: Flexible and Rigid Materials [12]

Vibration Reduction Methods: Flexible Connectors Currently in use at Soudan CDMS site.

Vibration Reduction Methods: Flexible Connectors

Vibration Reduction Methods: Active Cancellation [13]

Vibration Reduction Methods: Active Cancellation Single PipeFour PipesSix Pipes [7]

Conclusions Vibration of PT415 should be less than current GM cryocooler at Soudan Vibration of PT415 should be less than current GM cryocooler at Soudan More analysis needs to be done More analysis needs to be done Any of the suggested methods of reduction could be applied. Any of the suggested methods of reduction could be applied. Adding flexible materials--least work, but also least reduction Adding flexible materials--least work, but also least reduction Active cancellation--work intensive, but great reduction, may not dampen vibrations at high frequency Active cancellation--work intensive, but great reduction, may not dampen vibrations at high frequency

Works Cited 1. Reisetter, Angela. “ 1. Reisetter, Angela. “Results from the Two-Tower Run of the Cryogenic Dark Matter Search.” University of Minnesota “SuperCDMS Development Project.” SuperCDMS Collaboration. Proposal to DOE and NSF Radebaugh, Ray. “Development of the Pulse Tube Refrigerator as an Efficient and Reliable Cryocooler.” Institute of Refrigeration, London Courtney, Bill. “Cryocoolers-Refrigerators producing very low temperatures” Accessed on Cheshire Innovation. 5. Yuan, Sidney. “Pulse Tube Coolers (Cycle, Engines, Cryogenics Refrigerators, Cryocoolers).” Uchiyama, T., K. Kuroda, M. Ohashi, et al. “Present status of large-scale cryogenic gravitational wave telescope." Classic Quantum Gravity V Feb. 2004: p “Cryomech PT415.” Cryomech, Inc Uchiyama, T., K. Kuroda, M. Ohashi, et al. “Present status of large-scale cryogenic gravitational wave telescope." Classic Quantum Gravity V Feb. 2004: p “Cryomech PT415.” Cryomech, Inc Suzuki, T., T. Tomaru, T. Haruyama, et al. "Ultra-Low Vibration Pulse Tube Cryocooler with a New Vibration Cancellation Method." Advances in Cryogenic Engineering: Transactions of the Cryogenic Engineering Conference. V American Institute of Physics. 8. Tomaru, Takayuki; Toshikazu Suzuki; Tomiyoshi Haruyama; et al. "Vibration analysis of cryocoolers." Cryogenics. V44, p “Cryorefrigerators: Pulse Tube.” Cryomech Inc “Cryorefrigerators: Pulse Tube.” Cryomech Inc “Function of Piezoelectric Accelerometers.” PCB Piezotronics. PCB Group, Inc Veprik, A.M., S.V. Riabzev, G.S. Vilenchik, et al. “UItra-Iow vibration split Stirling linear cryogenic cooler with a dynamically counterbalanced pneumatically driven expander.” Cryogenics. V4, p Tomaru, Takayuki; Toshikaza Suzuki; Tomiyoshi Haruyama; et al. “Development of a Vibration- Reduction System of Cryocooler for a Cryogenic Interferometric Gravitational Wave Detector.” 13. Suzuki, T., T. Tomaru, T. Haruyama, et al. "Pulse Tube Cryocooler with Self-Cancellation of Cold Stage Vibration." Cryo Prague