Status Update on GRANIT Spectrometer at Les Houches (August 19, 2024)

GRANIT aims to increase observation time of neutrons in gravitational states and enhance precision of measurements. Details about the clean room, UCNs hunting, and progress made in 2010 are outlined, emphasizing the need for system reliability and improvement. Significant steps have been taken towards achieving resonant transitions between quantum states and higher statistics for better neutron observation. Advances in cryogenic systems and power circuits are also highlighted for future enhancements.

• GRANIT
• Spectrometer
• Neutrons
• Clean Room
• Cryogenic Systems

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1. GRANIT 2014 - Les Houches Status of the GRANIT Spectrometer August 19, 2024 Granit 2014 - Les Houches - Francis Vezzu 1

2. GRANIT - The aims For time being Longer observation time Resonant transition between quantum states can be observed Higher statistics due to a better source In the future Increase observation time of neutrons in gravitational states Storage of neutrons in a closed gravitational trap To dramatically increase the precision of measurements Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 2

3. UCNs Way ILL Reactor - Level C Monochromator Clean Room Reactor GRANIT Area Beam Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 3

4. UCNs Way Clean room Spectrometer Cryostat Source Neutrons Beam Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 4

5. Its better in 3d Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 5

6. Some Reminders In February 2010 Most of elements needed to build the spectrometer were ready Few months are expected to be needed to finish the assembly First results were expected by the end of the year Now where were we Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 6

7. The clean room In 2010 it was under construction ISO 7 366 m3/h ISO 4 ISO 6 13481 m3/h 1602 m3/h Now we have an ISO 4/5 clean room equipped with 3 pairs of Helmholtz coils and a gantry usable for handling. (Measured around the spectrometer, under laminar flux) Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 7

8. First steps in UCNs hunting We have got the Cryo - Source during autumn 2010 We began to perform tests on cryogenic system Several issues Difficulties to reach 0.8K in the conversion volume Problems due to the configuration of the new extraction However We measured few UCNs with a temporary mounting We did some measurements in a real configuration last year But we realize that we need to improve Reliability of the system to reduce frozen trouble and re-heating We mainly work on 3He and 4He circuits Cryogenic power to have some margin and to fix some technical issues Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 8

9. Cryostat, L4H Source, Extraction Replace the existing extraction by a new one Tests performed with the extraction connected outside the clean room to check performances of the cryo-source. Comparison of results for the two types of extraction. Dr Benoit Cl ment s talk : MonteCarlo simulations of the GRANIT UCN source and extraction system 2 stages cold head Top view of the cryostat Previous version of extraction UCN Source 10 liters of L4He @0.8K New extraction installed Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 9

10. UCNs detection A box located outside the clean room Connected with the extraction volume Filled with Argon 2 detectors can be used Measurements and results commented by D.Roulier Damien Roulier: Commissionning of the UCN source for GRANIT Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 10

11. Increasing Cryogenic power Old Outlet box of the cryostat with thermal screen @40K New one with N2 thermalization @77K . For tests Replacement of outlet box of the cryostat Replacement of thermal screens Adding cooling system Conversion volume Temperature T = 0.74K Adding cold head 150W@77K Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 11

12. The spectrometer Optical elements Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 12

13. Optic elements Planarity = 80 ?m Roughness mirrors = 1.5 Roughness absorber = 10 m DLC coating on extraction mirrors Resonant transitions Transport mirror with edges Absorber mirror Scatterer mirror 0,05< Slit < 0.2 mm Extraction mirror Adjustment micrometric screws Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 13

14. Optic Elements All the mirrors have been provided by SESO (Aix en Provence France) DLC Coatings have been performed by LMA (advanced material laboratory) Mechanical supports have been machined at LPSC Workshop Scatterer Mirror with DLC coating High roughness Transport mirror no DLC Support assembly Extraction Mirror with DLC coating Low roughness Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 14

15. Optical Elements - Installation 1-Extraction Mirror Installation The complete installation 2-Scatterer Mirror Installation Scatterer Mirror 3-Mirror Support Adjustment Extraction Mirror Tiltmeter Storage Volume 4-Transport Mirror Adjustment 5-Absorber Mirror Preparation 6-Absorber Installation Absorber Mirror Transport Mirror Adjustment of the mirror support Adjustment Support UCNs Detector with Cadmium shielding Piezo elements for adjustment of the absorber Piezo element Adjustment of the transport Mirror Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 15

16. Trap Mirror 3 mm 300 x 300 x 70 Planarity: 40 nm Roughness 0.5 rms Cost : 160k Provided by SESO (Aix en Provence) GRANIT Main Mirror on its support 12 edge mirrors are glued around the central mirror to do the trap. Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 16

17. Extraction guide Compensate misalignments and relative moves Drive UCNs from extraction to the mirrors Separate spectrometer vacuum from conversion/extraction volume Store UCNs Separating window Storage Volume Spectrometer Vacuum Bellows UCN Valve Guide Bellows Connection Transport mirrors Pumping Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 17

18. Neutron guide How we have made it Thin stainless steel off the shelf foils (0.05 mm) rolled inside calibrated tubes. DLC coating foreseen on foils but finally not performed Works for compensating misalignment Works for driving UCNs even the roughness of the surface are not excellent Difficult to install in the real configuration without damaging tube extremity As we don t need DLC coating anymore, a new solution with electro- polished stainless steel tube will be used for future runs Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 18

19. UCN Valve The UCN Valve is foreseen to close the storage volume for a defined time to permit the storage of UCN and avoid their return Controlled by a Lab view application It was installed on the experiment for the last measurement campaign UCN Valve Step by step motor Phytron VSS 25 UCN Valve + Motor Butterfly Flexible joint Nickel Coating Valve Open Close Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 19

20. Connecting the source and the spectro The goal is to link the exit flange of the conversion volume to the spectrometer vacuum flange the extraction volume to the storage volume We have to pass through a quite small window managed in the wall of the clean room and the biological shielding Hard job! The starting point on one side of the wall The flange to reach on the other side Less than 50 cm but however a long way to go Small hands are sometimes required ..and special tools too. Acrobatic and uncomfortable positions Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 20

21. Connecting the source and the spectro Finally the connection is completed on May 2013 Inside the vacuum chamber Inside the clean room Outside the clean room Storage volume connected to the extraction guide Vacuum chamber Cryostat Outlet box Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 21

22. Storing UCNs Use a Storage Volume square section with DLC coating Volume = 544 cm Windows for the connection of mirrors 3 Connection with the neutrons valve Aluminum plates coated with DLC At the moment A new version is under construction Massive copper Cylindrical inner shape Storage volume installed on the line Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 22

23. Separate the two vacuum volumes We need to separate the spectrometer vacuum from the extraction one to avoid heating in case of spectrometer openings The thinner the window, the lower the UCN losses. The foil must resist to an overpressure of 1.5 bar in both direction 2 half pieces milled by electro cutting- 0.25 mm ribs Titanium foil 0.015 of thickness Tested with success under vacuum and under 5 bars pressure. We suspect that foil to be a part of UCNs losses Transmission losses Damien Roulier: Commissionning of the UCN source for GRANIT Impurities deposit by cryo-pumping Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 23

24. Resonant Transitions Transition induced by a magnetic field gradient Principle The magnetic field gradient will be produced with a net of square wires (1 x 1 mm ) distant of 0.25 mm and located above the main mirror in which a 4A/mm permanent current will circulate. Dr Guillaume Pignol s talk : Excitation of transitions in GRANIT with time variation of magnetic field Dr Stefan Baessler s talk : Frequency shifts in gravity resonance spectroscopy Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 24

25. Resonant transitions 4 Magnetic field generator modules assembled and connected together 128 wires - Gap between wires : 0.25 mm 32 squared wires section 1mm With PCB Overheat 4 modules ready to be connected Massive circuit 50 W to be evacuated No convection Cooling system is required Circulating of cooled N2 + LN2 Heat exchanger a 128 wires net Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 25

26. Cooling of resonant transitions system Vacuum chamber N2 circulating - 2 x 9 m Heat exchanger in a LN2Vessel Tests performed in realistic conditions Under vacuum 5A Current Resonant transition system connected and installed in the vacuum chamber LN2 Vessel N2 Bottle Heat exchanger Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 26

27. Cooling of resonant transitions system Good results We can stabilize temperature of the wires quite easily Will be install in the spectrometer soon Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 27

28. Vacuum range Improve the vacuum range in the vacuum chamber of the spectrometer Stove the Granit Table under vacuum Outgassing Rinsing process ?.?? ?mbars Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 28

29. Adjustment and leveling Leveling of the table is done using 3 Piezo elements The table horizontality is controlled with tiltmeters located on the top surface The control system adjust it continuously Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 29

30. Adjustment and leveling Horizontality of each mirror is adjusted with 3 piezo elements Horizontality is controlled with tiltmeters located on mirror supports Mirrors adjustment is done using micrometrics screws Positioning is done using indicator (0.001) located at different places Piezo for absorber adjustment indicator P-239.9 svPiezo For transport mirror Adjustement ring Micrometric screw Piezo support Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 30

31. Adjustment and leveling Avoid any contact with mirror surfaces Design of a solution using an optic method of measurement Laser sensor could answer to the problem Tests are foreseen within 2 months If that succeed installation and using for the next runs Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 31

32. Control and command All the experiment is controlled and driven by Labview applications Control programs are ready and work Continuous table leveling Mirrors adjustment DAQ Valves control Protection system for vacuum and HV control is under development Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 32

33. Whats next From now to June Mounting of complete 3He circuit With metallic o rings Oil filtration system Mounting of extraction with modification Mounting new version of the storage volume Mounting of optical elements Installation of cooling system for resonant transition So rebuilt everything and start the experiment From June 2014 Data measurements Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 33

34. Thank You for your attention Granit 2014 - Les Houches - Francis Vezzu August 19, 2024 34