Overview of Cryostat Issues and Mitigation Plans Hogan

Flashlet History at Fermilab Noticed Big and periodic Vacuum P-Spikes In Lower Ring Two

Burp in the morning Dangerous Vacuum First Magnet Provisional Spikes 20 -24 hours Operating

Burp the evening before Second Provisional Mode (spoil vacuum intentionally) Ramp Magnet In the

Provisional Mode of Magnet Operation • Developed over a few weeks of study •

Review of Key Facts • Leak Rate at FNAL has been estimated to be

David Sweigart’s Technique Measured 6 e-3 Torr-liters/sec (Doc. DB 3262) Close OFF All Relevant

Repairing the Helium Leak Repair is nearly Done. Covered in Del’s Vacuum System Talk

Inner Ring of Charcoal Panels • We discovered their Location • We accessed their

Our Recommendation • Based on engineering drawings, info from BNL, and discoveries made with

Why Remove Panels ? • Panels were not intended to be used in the

Risks and Mitigation Vacuum Chamber Structural Integrity – Erik Voirin Instrumentation cables and LN

Risks and Mitigation (cont. ) Lower Ring vacuum pumping capacity without carbon panel -

Talk Agenda • • • Overview and Experience at FNAL: Hogan Experience at BNL:

Review Charge • Have we properly addressed the technical risks that are listed ?

Slides: 15

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Overview of Cryostat Issues and Mitigation Plans Hogan Nguyen Jan 9 th 2017

Flashlet History at Fermilab Noticed Big and periodic Vacuum P-Spikes In Lower Ring Two Quenches Due to Vacuum P-Spikes Magnet At Full Power Sept 2015 Oct 2015 Implemented First Provisional Mode of Running Leak Studies Nov 2015 Implemented Second Discovery Provisional Of Charcoal Mode of Panel Running Locations Dec 2016

Burp in the morning Dangerous Vacuum First Magnet Provisional Spikes 20 -24 hours Operating Mode Following burp (Avoid Occurrence of Vacuum Spikes) Red (0 -10 K) : Lower Ring Temperature Pea Green (0 - 10 micro. T): L 7 Vacuum Gauge Orange (0 -10 micro. T): L 11 Vacuum Gauge Blue (0 -10 micro. T): L 3 Vacuum Gauge Gray (0 -6000 A): Magnet Current L 7 and L 11 Gate Valve Open

Burp the evening before Second Provisional Mode (spoil vacuum intentionally) Ramp Magnet In the Morning Red (0 -10 K) : Lower Ring Temperature Pea Green (0 - 10 micro. T): L 7 Vacuum Gauge Orange (0 -10 micro. T): L 11 Vacuum Gauge Blue (0 -10 micro. T): L 3 Vacuum Gauge Gray (0 -6000 A): Magnet Current All Quench-Causing Vacuum Spikes are GONE Only small (non-fatal) vacuum spikes Remain

Provisional Mode of Magnet Operation • Developed over a few weeks of study • Regenerate Charcoal Panels in the Lower Ring (“burp”) every 2 days • Intentionally Spoil the Lower Ring Vacuum. Allows for safe operation during Magnet Shimming Provisional Mode not Good enough for Physics Run

Review of Key Facts • Leak Rate at FNAL has been estimated to be about 1 e-3 Torr-liters/sec while magnet is cold. Del’s Measurement David Sweigart’s Measurement • Leak Location has been Determined to be dominated by isolators in Lead Can. Del, Jake, Hogan measured in Fall 1025

David Sweigart’s Technique Measured 6 e-3 Torr-liters/sec (Doc. DB 3262) Close OFF All Relevant Gate Valves. Charcoal is the primary source of Pumping. Burp Magnet and Measure Volume of Gas Released from Charcoal

Repairing the Helium Leak Repair is nearly Done. Covered in Del’s Vacuum System Talk

Inner Ring of Charcoal Panels • We discovered their Location • We accessed their state This is an important Discovery, and is a new opportunity for us to reduce risk ! Covered in Karie Badgley’s Talk

Our Recommendation • Based on engineering drawings, info from BNL, and discoveries made with the fiber scope, we have developed a low risk plan to open the cryostat and remove the charcoal (Cary Kendziora). • Proceed with charcoal removal given the review panel’s recommendations and approval.

Why Remove Panels ? • Panels were not intended to be used in the first place (Bill Morse) • Marginal Panels are a big source of uncertainty (Erik Swanson, Del Allspach): Behavior of Marginal Panels is very hard to predict in the presence of leaks. If new leaks develop, this requires engineering, operations, and scientist effort to manage. These are scarce resources.

Risks and Mitigation Vacuum Chamber Structural Integrity – Erik Voirin Instrumentation cables and LN 2 Cooling Tube - Cary and Karie Compromised MLI and LN 2 thermal shield – Bob Sanders and Del Drilling with hole saw – Cary Vibrations - Erik Voirin Welding - Cary, Hogan, Erik V

Risks and Mitigation (cont. ) Lower Ring vacuum pumping capacity without carbon panel - Del, Jake Coil position – Hogan Schedule implications of removing charcoal now vs. 2017 Summer Shutdown - Chris

Talk Agenda • • • Overview and Experience at FNAL: Hogan Experience at BNL: Bill Morse Charcoal Panel Search: Karie Badgley Flashlet Working Model: Erik Swanson Plan for Removing the Panels: Cary Kendziora Deformation/Stress Analysis: Erik Voirin Cryostat Pumping System: Del Allspach Risks and Mitigation: Del Allspach Project Schedule Implications: Chris Polly Q&A Optional g-2 Ring Tour

Review Charge • Have we properly addressed the technical risks that are listed ? Additional risks that we should consider ? • Is the plan as presented reasonable and achievable in the time scale presented ? • Are the resources (personnel and M&S) adequate for the job ?