Momentum Compaction Factor Measurements in the Large Hadron Collider

The Large Hadron Collider (LHC) at CERN and its planned luminosity upgrade, the High Luminosity LHC (HL-LHC) demand well-controlled on- and off-momentum optics. Optics measurements are performed by analysing Turn-by-Turn (TbT) data of excited beams. Different techniques to measure the momentum compaction factor from these data are explored, taking into account the possibility to combine them with RF-voltage scans in future experiments

Postoperative Pain after Different Transscleral Laser Cyclophotocoagulation Procedures

Background: As the number of surgical options in glaucoma treatment is continuously rising, evidence regarding distinctive features of these surgeries is becoming more and more important for clinicians to choose the right surgical treatment for each individual patient. Methods: For this retrospective data analysis, we included glaucoma patients treated with either continuous wave (CW-TSCPC) or micropulse transscleral cyclophotocoagulation (MP-TSCPC) in an inpatient setting. Pain intensity was assessed using a numeric rating scale (NRS) ranging from 0 (no pain) to 10 (worst imaginable pain) during hospitalization. CW-TSCPC was performed using OcuLight® Six (IRIDEX Corporation, Mountain View, CA, USA) and MP-TSCPC was performed using the IRIDEX® Cyclo-G6 System (IRIDEX Corporation, Mountain View, CA, USA). Results: A total of 243 consecutive cases of TSCPC were included. Of these, 144 (59.26%) were treated with CW-TSCPC and 99 (40.74%) with MP-TSCPC. Using the univariable model, the risk for postoperative pain was observed to be lower in MP-TSCPC compared with CW-TSCPC (unadjusted: OR 0.46, 95% CI 0.24–0.84, p = 0.017), but this did not hold using the multivariable model (adjusted: OR 0.52, 95% CI 0.27–1.02, p = 0.056). Simultaneously conducted anterior retinal cryotherapy was associated with a higher risk for postoperative pain (OR 4.41, 95% CI 2.01–9.69, p < 0.001). Conclusions: We found that the occurrence of postoperative pain was not different in CW-TSCPC compared with MP-TSCPC in a multivariable model. In cases of simultaneous anterior retinal cryotherapy, the risk for postoperative pain was significantly higher

Second-order dispersion measurement in LHC

The quadratic dependence of the orbit on the relative momentum ofset, also known as second-order dispersion, is analysed for the first time for the LHC. In this paper, the measurement and analysis procedure are described. Results and implications on future optics are discussed

Optics Correction Strategy for Run 3 of the LHC

The Run 3 of the LHC will continue to provide new challenges for optics corrections. In order to succeed and go beyond what was achieved previously, several new methods to measure and correct the optics have been developed. In this article we describe these methods and outline the plans for the optics commissioning in 2022

Optics Correction Strategy for Run 3 of the LHC

After more than 3 years of shutdown the LHC is again operational in 2022. Experience from the previous Long Shutdown (LS) has shown that the local errors in the triplet quadrupoles changed significantly between Run 1 and Run 2, and first measurements in 2022 unveil further changes. In the LHC, feed-down from the Interaction Region (IR) non-linear corrections to linear errors requires an iterative approach between the two types of corrections. In this article we describe the key measurements and corrections performed in 2021 and 2022 until the write-up of this report

Optics Measurement by Excitation of Betatron Oscillations in the CERN PSB

Optics measurement from analysis of turn-by-turn BPM data of betatron oscillations excited with a kicker magnet has been employed very successfully in many machines but faces particular challenges in the CERN PSB where BPM to BPM phase advances are sub-optimal for optics reconstruction. Experience using turn-by-turn oscillation data for linear optics measurements during PSB commissioning in2021 is presented, with implications for the prospect of such techniques in the PSB more generally

Optics Measurements and Correction Plans for the HL-LHC

The High Luminosity LHC (HL-LHC) will require stringent optics correction to operate safely and deliver the design luminosity to the experiments. In order to achieve this, several new methods for optics correction have been developed. In this article, we outline some of these methods and we describe the envisioned strategy of how to use them in order to reach the challenging requirements of the HL-LHC physics program

Progress of the FCC-ee optics tuning working group

International audienceFCC-ee is a proposed lepton collider with a circumference close to 100 km to produce an unprecedented amount of luminosity. The FCC-ee optics tuning working group is addressing one of the most critical aspects of the FCC-ee, that is the recovery of the optics design performance in presence of realistic imperfections. Various teams from laboratories all around the world have got together to assess field quality tolerances and review and share experience gained at synchrotron light sources and lepton colliders such as SuperKEKB. This paper reports the latest results on optics measurements and tuning simulations for various techniques, the development of simulation tools, and possible layout design changes to optimize the tuning performance

The 2018 heavy-ion run of the LHC

The fourth one-month Pb-Pb collision run brought LHC Run 2 to an end in December 2018. Following the tendency to reduce dependence on the configuration of the preceding proton run, a completely new optics cycle with the strongest ever focussing at the ALICE and LHCb experiments was designed and rapidly implemented, demonstrating the maturity of the collider’s operating modes. Beam-loss monitor thresholds were carefully adjusted to provide optimal protection from the multiple loss mechanisms in heavy-ion operation. A switch from a basic bunch-spacing of 100 ns to 75 ns was made as the beam became available from the injector chain. A new record luminosity, 6 times the original design and close to the operating value proposed for HL-LHC, provided validation of the strategy for mitigating quenches due to bound-free pair production (BFPP) at the interaction points of the ATLAS and CMS experiments. Most of the beam parameters of the HL-LHC Pb-Pb upgrade were attained during this run and the integrated luminosity goals for the first 10 years of LHC operation were substantially exceeded

Optics Measurement and Correction Strategies for HL-LHC

The baseline strategy for optics commissioning in the HL-LHC era is presented and reviewed in detail, along with recent developments and unsolved matters in the linear and nonlinear optics measurement and correction techniques