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Weekend Update: Beam Positioning, Alignment, and Loss Mapping at TCTs

On Saturday, September 18, significant progress was made in beam positioning and alignment at the TCTs. Smooth orbital control was maintained with a maximum excursion of ~0.2 mm at TCT. Injection protection qualifications and TCDI acceptance measurements yielded positive results. Loss maps for both beams were created, showing acceptable hierarchy levels. Quench level measurements indicated no quenching under test conditions, although some QPS issues were noted. Overall, preparations for upcoming collisions continue with thorough evaluations and optimizations.

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Weekend Update: Beam Positioning, Alignment, and Loss Mapping at TCTs

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  1. Saturday 18.9 • Morning: • Squeeze and collide. • Smooth, orbit rather well under control (max. excursion ~ 0.2 mm at TCT, roughly 0.5 -1sigma). Orbit evolution at the TCTs recorded – to be analysed in details. • All IRs were optimized, then offset for ALICE. • Beam-based alignment of all TCTs for collisions. • TCSG in IR6 was rechecked. TCSG B1 center shifted by 0.4 mm (~0.5 sigma). • 15:30 Loss maps in collisions • Loss maps for betatron losses were made for both beams (i.e. B1v, B1h, B2v, B2h) – no surprises, hierarchy looks ok. To be checked in detail offline. • Beams were dumped (the left over of) B2, when trying to perform momentum losses. 8:30 meeting

  2. Beam positions at TCTV 7 m  3.5 m 8:30 meeting

  3. Beam position at TCTVB.4L8 during separation bump (V) collapse 8:30 meeting

  4. B1 V loss map in collision 8:30 meeting

  5. B1 V loss map – zoom into IR7 8:30 meeting

  6. Saturday 18.9 • 17:00 Injection protection qualification • TCDI acceptance remeasured for TI 2 V - results look good, and the coverage for both lines is in tolerance. Problem in the week was a bad knob. • Scanned injected beam at TDI and TCLIs - some offset seen of the order of 1 sigma - maybe due to the differences in the LHCFAST1 and LHC3 trajectories in the lines - data to analyse in detail but no big surprises are apparent. • Tripped both ALICE and LHCb BCMs when beam hitting TDI - coincided in all cases with LHC BLMs above dump thresholds. 8:30 meeting

  7. Injection protection 8:30 meeting

  8. Saturday 18.9 • 21:00 Quench level measurement at injection • Bump (inwards as B1 on inside) at 14R2.B1. • Beam in inject and dump mode. • No quench was produced, even with ~8E9 p/bunch and bump amplitudes of around 24 mm, but QPS problem on old QPS ! • Need access to reset controller. Probably controller reacted to the radiation. • 02:00 Access to Pt2. • Lost communication between LASS and LACS. • Finally access at 03:00. • 05:00 Injection • Asynch. dump test at injection. 8:30 meeting

  9. The plots show one of the highest registered losses (transient losses). The values on the first and the second monitor on MQ is up to factor 3 above calculated quench level. A global view shows structure of losses following the lattice in a particular way. No loss is registered after cleaning insertion in IR3 (plot starts left of IP2 and ends right of IP3). • 20 uSv/h on contact at MB.C14.R2. 8:30 meeting

  10. Loss maps and asynch dump tests • Missing loss maps: • Collision settings: • Positive off-momentum B1+B2 • Negative off-momentum B1+B2 • Further still to be qualified: • Re-check negative off-momentum for 100urad settings for B2 (hierarchy problem seen before) . • Full set of loss maps for end of squeeze, separated beams (B1v, B1h, B2v, B2h, positive off-momentum B1+B2, negative off-momentum B1+B2). • Plus the asynchronous dump tests… 8:30 meeting

  11. Today • Ramp, squeeze, collide cycles • Loss maps, asynchronous dump tests. • Prepare and test all collimator functions • SPS scrapper to be fixed… 8:30 meeting

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