Answers to committee questions magnets DOE Review 622011

Answers to committee questions - magnets DOE Review, 6/2/2011 Answers to Committee Questions – Magnet Systems

Q 1: Please clarify the definition of success for the operating point vs. short sample limit 1) Background: • Last year following a review recommendation we established a CERN-US working group to discuss requirements and development plans for Nb 3 Sn and present recommendations to LARP, DOE, and CERN management • One of the goals was to articulate a set of “success criteria” for magnet quench performance since it was felt that simply defining a target gradient as it was done for TQ/LQ (200 T/m) would not capture some of the key metrics such as fast training and no retraining after a thermal cycle • Also, in order to apply to any magnet they were formulated relative to a maximum theoretical performance given the magnet design and conductor properties • The committee expressed concern about the statement that Target operational quench level will be defined as 80% of SSL • A wording issue? “Operating point” suggests operation in the machine; “short sample limit” does not have a unique definition DOE Review, 6/2/2011 Answers to Committee Questions – Magnet Systems

Q 1: Please clarify the definition of success for the operating point vs. short sample limit (slide 2/3) 2) Clarification attempt: • This definition of success only applies to quench performance in R&D models – not to the design/expectations for HL-LHC • We define theoretical performance limit as the intersection of the magnet load line (peak field in the conductor as a function of current) and the cable critical current as function of field • The conductor peak field is derived from calculations and the cable critical current is derived from extracted strand measurements using the ITER Ic measurement method • The performance limit as defined above provides a maximum current that the magnet can sustain without quench. We take 80% of this value as a reference point in evaluating the magnet quench performance • The 80% criteria will provide a reference gradient and peak field. • The goals for training/retraining stay the same • We will review with CERN to make sure we are on the same page DOE Review, 6/2/2011 Answers to Committee Questions – Magnet Systems

Q 2: HQ – Please list issues to be addressed and the focused remediation steps The causes of observed performance limitations: • • Coils under excessive compaction during curing and reaction Insufficient insulation between coil and ground Remediation: • • • Reduce strand cable size Room for 4. 5% of azimuthal coil expansion Room for 2. 3% of radial coil expansion Room of 4 mm/m (Island gap size) for coil axial contraction Thicker insulation between layers Improved electrical QA - Impulse test DOE Review, 6/2/2011 Answers to Committee Questions – Magnet Systems

Q 3: How are the HQ and LHQ schedules integrated? (slide 1/2) LQS 03 test HQ coil w new cable tested w mirror HQ 02 w new cable Practice coils Spare coil test Structure develop. & test LHQ 01 coils LHQ 01 assembly & test LHQ 01 b assembly & test LHQ 02 coils, assembly & test DOE Review, 6/2/2011 Answers to Committee Questions – Magnet Systems

Q 3: How are the HQ and LHQ schedules integrated? (slide 2/2) LQS 03 test HQ coil w new cable tested w mirror HQ 02 w new cable Practice coils Spare coil test LHQ 01 coils DOE Review, 6/2/2011 Answers to Committee Questions – Magnet Systems

Q 4: What are the deliverable goals of the magnet program and how are you going to measure them? • Goal of LARP is to demonstrate Nb 3 Sn technology for use in the upgraded IR quads. Therefore LARP will have achieved its goal if the HL-LHC TDR will specify a Nb 3 Sn IR Quad ØClearly we are on the right track since Nb 3 Sn is now recognized as the primary candidate technology for the upgrade • We agreed with CERN that a successful LHQ with 120 mm aperture and ~4 m length will be sufficient to complete this demonstration • We agreed on a set of success criteria for LHQ quench performance • However other key performance indicators/targets are not yet defined: field quality, thermal margin, radiation resistance etc. ØDefining these targets for LHQ is not a goal of the design study, but the design study will help understand what is needed ØDirect comparison between Nb 3 Sn and Nb. Ti models with 120 mm aperture will also be an important decision criteria DOE Review, 6/2/2011 Answers to Committee Questions – Magnet Systems

Q 4 follow up: so why do we discuss infrastructure needs, construction schedules etc? • There seems to be an implicit mandate or expectation that LARP will facilitate the construction planning until it is handed off to a project • Last year’s review contained many recommendations pushing us in this direction. • A legitimate question is whether some of these preparation steps would then become LARP tasks or not • Examples: long infrastructure for the prototype, early conductor procurements, short model of the final design, the prototype itself • Some guidance from the APUL (then LAUC) experience: LARP developed the proposal, but the 2008 DOE review of LARP strongly recommended to form a separate organization asap. • However, there are some important differences in this case since HLLHC IR Quads are fully aligned with LARP while the “Phase 1” scope was not, especially for magnets DOE Review, 6/2/2011 Answers to Committee Questions – Magnet Systems