LHC Beam Cleaning Study Group - Planning |
General - Planning - List of tasks - Old work list
Not all the work listed is done within the LHC beam cleaning study group but may be done in other working groups or specific CERN groups. However, the results are required for the proper design of the LHC collimation system.
The LHC collimation system was reviewed at the BI review 2001. The input provided by the review was summarized (WORD, PDF). This document summarizes the status of the system in November 2001, providing a basis for the further directions of our work.
Timeline: Improved system until November 2002
Preliminary planning of timeline and resources:
A possible schedule with associated resources was put together and can be viewed here:
Excel file or see below
| Task | Schedule | People | Details |
| Collimator specification | 15.1.02 | all | Specify beam loss to be accepted without damage (steady loss due to lifetime, fast loss due to irregularities). Present to LCC. |
| Analysis of asynchronous firing of beam dump | 15.1.02 | JBJ | Analyze the consequences of an asynchronous firing of one or more dump kicker modules. |
| Dynamic effects during ramp and squeeze. | tbd | MH, RA | Predict changes of beta function, coupling, orbit, emittance, … during the snapback and the squeeze. |
| CERN meeting on Collimators and Beam Absorbers | second half January 2002 | Beam Cleaning Study Group + CERN experts | Address the questions: What collimators and beam absorbers can stand the impact of part of LHC beam in case of equipment failure? What collimators can stand the heating by continuous loss of particles? What are the consequences for the beam intensities and lifetime? |
| Conceptional design of an improved collimation system. | February 2002 | all | Weighing of different options. Additional collimators or change of existing collimators? Lighter material and longer or better geometry or both? Identify most promising option. |
| Study of a collimator technical design with better material, improved geometry | Start: February 2002 | GB, CF, RJ | Based on the outcome of the expert meeting do a first design for a more robust collimator. Specify expected imperfections. |
| More tools for cleaning efficiency with multiple imperfections. | March 2002 | RA, DK | Further develop tools for estimating cleaning efficiency. Include orbit errors, chromatic effects, non-linear fields, … |
| Insertion design with longer collimators: Possibilities and constraints. | tbd | JBJ, DK | Prepare possible optics solutions with more space for longer collimators. |
| Orbit stability. | tbd | JW | Expected orbit stability (fast and slow). Effect of a power supply with strong ripple? |
| Operational scenarios for running with collimators. | tbd | ML, JW, RA | How to run with collimators during an LHC cycle? Compatibility of machine measurements/procedures with collimation? Collimator control during ramp and squeeze? |
| Halo population and diffusion speed. | tbd | RA, FS | Expected diffusion speed in the LHC. Expected population of the LHC beam halo. Can we understand/predict it to the 1e-5 level? |
| RF timing problems. | tbd | JBJ | Beam loss into the abort gap after loss of RF timing. Consequences for the collimation system? |
| Impedance from the collimation system. | tbd | JBJ, DB, LV | Estimate of the impedance from the collimation system. Constraints on the collimator geometry! |
| Showering studies for predicting activation in the cleaning insertions. | MB (TIS) | Expected radioactivity in the cleaning insertions. Dependence on material, collimator length and spacing, shielding requirments, etc. | |
| Irregular beam loss (failures) and resulting beam loss in the cleaning insertions and downstream of the collimators. | tbd | VK, RS, RA | Develop different failure scenarios. Calculate the beam loss at the collimators during the failure. Simulate the particles escaping the collimation system and their propagation through the machine. Where are they lost? |
| Showering studies for heat maps and prediction of Beam Loss Monitor signals. | tbd | IB, JBJ | Development of showers in the cleaning insertions. Heating of collimators (damage). Prediction showers in the BLM's. |
| Use of BLM signals for machine protection. | tbd | BD, EG | Analyze BLM signals from regular and irregular beam loss scenarios. Include detailed geometry and shower development. Construct reliable dump triggers from typical signatures in beam loss. |
| Damage due to injection oscillations? | tbd | HB | Expected maximum amplitude of injection oscillations for different phases? Protection against injection oscillations? |
| Use of quadrupolar BPM's for beam size control during ramp and squeeze. | tbd | RA, MH | Fast and continuous monitoring of emittance and beta beat with quadrupolar BPM's. Expected accuracy and applicability for keeping the collimation system optimal? |
| Damage calculations for regular and irregular beam loss. | tbd | ? | Run state-of-the-art simulations for the damage of collimator jaws. Include heating, heat flow, shock waves, mechanical stress, etc… |
| Analyze catastrophic beam loss scenario. | tbd | ? | Will the collimation system stop a badly missteered beam? Will the first bunch create a hole for the rest of the bunch train, that goes through unperturbed? Where will the beam end up? |
| Effect from RF ripple. | tbd | ? | Effect from RF ripple on the beam loss rate? |
| Use of crystals for collimation. | tbd | ? | |
| Experimental tests of collimator design | tbd | GB, CF, RJ | Experimental tests on collimator heating, deformation, damage, destruction. |
| Machine experiments on collimation issues | tbd | RA, JBJ | Experiments on collimation issues and verification of calculated cleaning efficiency in existing colliders (HERA, RHIC, Tevatron). |
- Review sources of continuous beam loss, expected loss rates and diffusion speed.
- Establish and prioritize relevant collimation scenarios (injection, ramping, physics, collimation depth).
- Predict the cleaning efficiency in the presence of imperfections for the different scenarios.
- Study beam losses from transient effects, including magnet failures.
- Establish tolerances for beam parameters (beta beat, orbit stability) and components (collimator setting
accuracy, collimator smoothness, collimator alignment, local BPM's, ...)
- Develop and simulate operational scenarios.
- Work out a specification for the beam loss monitors.
- Beam size control during the ramp.
- Collimation control as a function
of beam size.
- Impedance from the collimators (D. Brandt et al once a collimator design is
available).
- Operational procedures.
- The primary role of collimation: protection or cleaning?
- Collimator surface roughness.
- Thermal effects.
- Orbit stability with power ripple.
- Ramp effects.
- Diffusion speed.