Instrumentation for Dynamic Nuclear Polarization. Alexander Barnes Massachusetts Institute of Technology Francis Bitter Magnet Laboratory

Transcription

1 Instrumentation for Dynamic Nuclear Polarization Alexander Barnes Massachusetts Institute of Technology Francis Bitter Magnet Laboratory

2 380 MHz / 250 GHz DNP Apparatus cryogenic sample eject 250 GHz gyrotron 9 Tesla NMR magnet microwave waveguide cryogenic MAS DNP probe heat exchanger Extensive instrumentation is required for Dynamic Nuclear Polarization

3 Cryogenic MAS DNP Probe cryogenic sample exchange robust MAS at 80 Kelvin with N2 optical sample illumination 250 GHz microwave channel cryogenic MAS DNP probes combined with high-power gyrotrons offer tremendous gains in sensitivity detailed CAD drawings posted at Conferences/program/64 (link at bottom of page) A. Barnes, January 2010; slide 3 Barnes et al., J. Mag. Res., 2009, 198 (2),

4 MAS DNP Probe Top Overview 4 mm stator eject pipe the 4 mm stator is retrofitted with a custom sample ejection pipe A. Barnes, January 2010; slide 4 Barnes et al., J. Mag. Res., 2009, 198 (2),

5 MAS DNP Probe Top Overview magic angle adjustment optical cryogenic temperature sensor (Neoptix) MAS detection drive cup bearings optical fiber for in situ sample illumination waveguide miter the probe design enables robust magic angle spinning at 80 Kelvin and 6 KHz while accommodating optical and microwave illumination of the sample A. Barnes, January 2010; slide 5 Barnes et al., J. Mag. Res., 2009, 198 (2),

6 Quadruple resonant RF circuit 1 H Schaeffer-McKay transmission line 13 C 15 N 1 H 15 N 13 C RF performance isolation 380 MHz; 1 H! B 1 = 120 KHz 96 MHz; 13 C! B 1 = 100 KHz 39 MHz; 15 N! B 1 = 95 KHz The probe efficiently couples 4 RF frequencies to the sample A. Barnes, January 2010; slide 6 Barnes et al., J. Mag. Res., 2009, 198 (2),

7 Modifications for Cryogenic MAS outer conductor: s.s. 321 chemical etch, electroplated with silver and gold flash finger-stock 6 stainless electroplated s.s. thermal break The transmission line thermally isolates the tuning and matching capacitors from the harsh cryogenic environment at the probe top A. Barnes, January 2010; slide 7 Barnes et al., J. Mag. Res., 2009, 198 (2),

8 250 GHz Microwave Channel waveguide miter corrugated inner conductor teflon window corrugated transmission lines, miterbends, and quasioptical components deliver ~5 Watts of microwave power to the sample A. Barnes, January 2010; slide 8 Barnes et al., J. Mag. Res., 2009, 198 (2),

9 millimeters millimeters Microwave Illumination of Sample (with Emilio Nanni) Dr. Björn Corzilius 6 4 grooved drivetip with epoxy sapphire (300 W/mK) bearing (80 Kelvin) millimeters Kel-F spacer (~0.5 W/mK) A. Barnes, January 2010; slide 9 sample 0-80 thread ~5 Watts of 250 GHz radiation is launched from the corrugated waveguide as a gaussian beam millimeters 10 12

10 Cryogenic Magic Angle Spinning cryogenic sample eject cryogenic MAS DNP probe heat exchanger

11 Heat Exchanger flexible vacuum jacketed transfer lines bayoneted connections rigid vacuum jacketed transfer lines liquid N2 reservoir at ambient pressure pressurized copper can heat exchange liquid level the pressurized can prevents liquification and enables spinning at 80 Kelvin the pressure in the can determines the liquid level and cooling capacity A. Barnes, January 2010; slide 11 Allan et al., J. Mag. Res., 1991

12 Can Oven and Transfer Lines can creates a cold oven fiberglass outer tube 50 W heater under PID control pump-out port accessible during operation the cryogens are vacuum insulated from the inside of the heat exchanger to the top of the probe A. Barnes, January 2010; slide 12 Barnes et al., J. Mag. Res., 2009, 198 (2),

13 Dewar with a Bellowed-hole o-ring seal threaded connection gore-tex seal on can the non-magnetic dewar has a bellowed hole to accommodate the sample ejection tube (Precision Cryogenics, Inc.) A. Barnes, January 2010; slide 13 Barnes et al., J. Mag. Res., 2009, 198 (2),

14 Robust Ejection Strategy Room temperature ~20 psi nitrogen gas entering from the exhaust line forces the rotor out of the stator, EVERY TIME! not a single rotor has been stuck inside the probe in over 18 months of operation A. Barnes, January 2010; slide 14

15 Sample Eject Path A. Barnes, January 2010; slide 15

16 Ejection Valve and Gently Slowing the Rotor teflon tube remotely controlled air piston o-ring seal not a single rotor has been damaged from the sample ejection system in over 18 months of operation (>100 ejections) A. Barnes, January 2010; slide 16 Barnes et al., J. Mag. Res., 2009, 198 (2),

17 Excellent Resolution at 90 Kelvin n-formyl-methioyl-leucyl-phenylalanine-oh LC FC MC C chemical shift (ppm) two backbone conformations are present at 82 Kelvin A. Barnes, January 2010; slide 17 Barnes et al., J. Mag. Res., 2009, 198 (2),

18 Sub-angstrom Precision and Accuracy DNP allows the sub-angstrom precision measurement of distances in membrane proteins in their actual native environment A. Barnes, January 2010; slide 18 Barnes et al., J. Mag. Res., 2009, 198 (2),

19 Accelerated Data Collection e - e - e - e - e - e - Proton T 1 in U- 13 C, 15 N br ~50 Å e - e - e - e - e - e - e - e - =biradical polarizing agent!- 15 N-bR N Chemical Shift (ppm) 50 mm TOTAPOL does decreases the optimal recycle delay to 1.6 seconds without not compromising resolution in the active site A. Barnes, January 2010; slide 19

20 M o in 15 N!"Lys br Span 622 ppm Skew # ppm # ppm # ppm # i ppm +2 sideband intensity corresponds to an effective molecule weight of 700 kda DNP allows precise measurement of CSAs in the active site of br A. Barnes, January 2010; slide 20

21 New 250 GHz Gyrotron Jagadishwar Sirigiri water-cooled collector ) mode converter + cavity $ Gun/cathode CAD is an integral tool for gyrotron design A. Barnes, January 2010; slide 21 with Sirigiri and Temkin

22 Gun Design (Jagadishwar Sirigiri & Ivan Mastovsky) stainless steel to copper braze joint stainless steel to ceramic epoxy joint ceramic break source: ISI(insulator seal) electron beam ground -12 kv 0 kv cathode (source: -12 kv Semicon, Kentucky) The gun is the source of the electron beam A. Barnes, January 2010; slide 22

23 Interaction Cavity much of the power in the electron beam is stored in the cyclotron motion of the electrons magnetic center The cavity dimensions are important in defining the mode of operation and frequency A. Barnes, January 2010; slide 23

24 Vlasov Launcher and Mode Converter (Jagadishwar Sirigiri) mirror 3 window quasi-elliptical mirror mirror 2 A. Barnes, January 2010; slide 24

25 Vlasov Launcher and Mode Converter (Jagadishwar Sirigiri) The 3 mirror assembly has proven to be an effective, robust design for the 460 GHz tube A. Barnes, January 2010; slide 25

26 Vlasov Launcher and Mode Converter (Jagadishwar Sirigiri) A. Barnes, January 2010; slide 26 The mode converter outputs a gaussian beam

27 Acknowledgments Thesis Advisor: Robert G. Griffin Collaborators: Jagadishwar Sirigiri Richard Temkin Judith Herzfeld (Brandeis) Evgeny Markhasin Antonio Torrezan Emilio Nanni Melody Mak-Jurkauskas Yoh Matsuki Technical Staff: Ronald DeRocher Ajay Thakkar Jeff Bryant Mike Mullins Grants: National Science Foundation Graduate Research Fellowship NIBIB Grants EB , EB , EB , EB , and EB Björn Corzilius Loren Andreas

28 Thank you for your attention!