LHC related Experiments proposed by CERN F. Schmidt,
LHC related Experiments proposed by CERN F. Schmidt, CERN Accelerator Advisory Committee Workshop Fermilab 28-30.07.2010 7/28/2010 Cern List of Experiments: F. Schmidt 1 CERNs Interest in Experiments at the Tevatron The first basic LHC Commissioning went well. The main issues to reach design luminosity are yet ahead of us! ==> Main source of interest! Demand for physics make machine studies increasingly difficult already now.
We learn a lot during commissioning but LHC itself is not a testbed for many studies. Many CERN beam tests for LHC being done at SPS. However, SPS not very close to LHC. Tevatron, at end of its useful life, could be by far better machine to study critical issues. 7/28/2010 Cern List of Experiments: F. Schmidt 2 Tevatron: Testbed Low diffusion beams
Super-conducting magnets Collisions and beam-beam effects Many instruments 7/28/2010 AC dipole crystal collimation hollow e-beam lens
e-beam lens BB compensator BPM resolution 20 much better than at the LHC! Tests with limited risk could be done with last Tevatron beam. Cern List of Experiments: F. Schmidt 3 Tevatron: Limits as LHC Testbed Difference in beam parameters Machine layout Hardware
In particular (incomplete): One Ring Unequal beam intensity Less bunches Much smaller machine Consequences for experiments E.G. How independent can one steer or excite the beams
==> Case by case check required for all experiments 7/28/2010 Cern List of Experiments: F. Schmidt 4 Latest List of Experiments proposed by CERN 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Tests of hollow e-beam scraping of proton beams for improved LHC collimation. Tests of crystal-based halo cleaning for improved LHC collimation. Tests of luminosity leveling with dynamic beta squeeze or crossing angle variation for future LHC performance upgrades ("HL-LHC"). Measurements of equilibrium proton beam distribution for improved benchmarking of diffusion and halo models.
Beambased measurements of the collimators transverse impedance for an improved benchmarking of the impedance models used for the LHC. Measurements of intra-beam scattering (IBS) with various intensities for improved benchmarking of IBS theory and models. Measurements of beam-beam resonances using an AC dipole. Measurements of beam-beam effects with various harmonic transverse perturbations for improved benchmarking of emittance growth models and in view of future LHC crab cavities. Measurements of beam-beam effects for different schemes of transverse bunch splitting. Collisions with large Piwinski angle, and possibly with longitudinally flat bunches. 7/28/2010 Cern List of Experiments: F. Schmidt 5 Type of Experiments NO Short Description Responsible Coll.
BB 1 Hollow e-beam R. Assmann x 2 Crystal Collimation R. Assmann x 3 Luminosity Leveling R. Assmann F. Zimmermann 4
Diffusion & Halo R. Assmann x 5 Collimator Impedance E. Metral x 6 IBS F. Zimmermann 7 BB & AC-Dipole R. Miyamoto R. Toms F. Schmidt
x 8 BB Emittance Growth F. Zimmermann x 9 BB Bunch Splitting M. Giovannozzi x 10 Large Piwinski Angle F. Zimmermann x
7/28/2010 Upgrade General x Cern List of Experiments: F. Schmidt x x x x 6 No 3: Tests of luminosity leveling with dynamic beta squeeze or crossing angle variation for future LHC performance upgrades ("HL-LHC"). Contact: R. Assmann & F. Zimmermann Motivation: To keep the event pile up acceptable and/or to control the beambeam tune shift luminosity leveling through dynamic beta squeeze or crossing angle variation is a key component of the High-Luminosity LHC. Experiment: Compensate pbar burn off by reducing beta* or crossing angle in physics store to level either the luminosity or the beam-beam tune shift. The beta* experiment would presumably start with a beta* much larger
than nominal, zero crossing angle and one or two bunches per beam (to avoid complications with long-range beam-beam effects). The crossing angle experiment would be done at the nominal squeezed beta* (if the IR aperture is sufficient), again with few bunches. The crossing angle could be controlled by changing the settings of the electrostatic separators, and the tune shift be observed through the Schottky monitors e.g. Questions: Can one adiabatically vary beta* and/or crossing angle when the beams are colliding? 7/28/2010 Cern List of Experiments: F. Schmidt 7 No 6: Measurements of intra-beam scattering (IBS) with various intensities for improved benchmarking of IBS theory and models. Contact: F. Zimmermann Experiment: IBS benchmarking - measuring the horizontal, vertical and longitudinal emittance growth rates at injection and top energy as a function of longitudinal (and transverse) emittance. This could be done with a single non-colliding bunch. Comparison with analytical and numerical predictions. Remark: It seems that this could be done relatively easily
at the Tevatron and such a careful IBS benchmarking could be indeed of general interest! 7/28/2010 Cern List of Experiments: F. Schmidt 8 No 7: Measurements of beam-beam resonances using an AC dipole. Contact: R. Miyamoto, R. Toms and F. Schmidt Experiment: Measurements of beam-beam effect in hadron colliders is not an easy task and we want to take this rare opportunity to try it out on the Tevatron. When the sustained large oscillations of the AC dipole are recorded by the BPM system of the Tevatron, with noise level of ~20 and a memory size of ~8,000 turns, we can observe small perturbations of betatron motion. We propose a direct measurement of nonlinear beam-beam resonances in the Tevatron. Questions: Can one kick the pbar beam sufficiently independently from the protons? An easy way is to have different tunes for both beams so that the AC dipole is most effective for the pbars. To be studied 7/28/2010
Cern List of Experiments: F. Schmidt 9 AC Dipole Simulations (R. Miyamoto) 7/28/2010 Cern List of Experiments: F. Schmidt 10 Line spectrum showing BB resonances ---- NO BB ---- with BB 7/28/2010 Cern List of Experiments: F. Schmidt 11 No 8: Measurements of beam-beam effects with various harmonic transverse perturbations for improved benchmarking of emittance growth models and in view of future LHC crab cavities.
Contact: F. Zimmermann Experiment: For the measurements with various harmonic perturbations. This needs colliding beams, and injection of the transverse harmonic noise (through the transverse damper) at different frequencies, inside and outside the betatron frequency spread, and in different frequency regimes (Hundreds of Hz, kHz, and tens of kHz), and ideally at different 'noise amplitudes. Remarks: Is this as easy as it seems? However this might be very time consuming and one has to ensure that the results are reproducible. 7/28/2010 Cern List of Experiments: F. Schmidt 12 No 9: Measurements of beam-beam effects for different schemes of transverse bunch splitting. Contact: Massimo Giovannozzi Experiment: Recently the effect of crossing a stable resonance was used to extract beam over a few turns. This generates a special structure in the transverse phase space, as the beam is split into various beamlets depending on the order of the resonance being used. This effect was
studied theoretically to propose a novel injection process aimed at reducing the space charge effects by shaping the transverse beam distribution. The current proposal aims at testing in the Tevatron the transverse splitting process and to measure the difference in beambeam effects between standard Gaussian beams and split beams in the transverse (horizontal) plane. Questions: : It seems to be a challenge to produce a large island structure in phase space without spoiling the other beam. Moreover the other beam is supposed to serve as the BB force. This will need some critical input by Tevatron experts. 7/28/2010 Cern List of Experiments: F. Schmidt 13 Novel multi-turn extraction - III Simulation parameters: Hnon-like map (i.e. 2D polynomial degree 3 mapping) representing a FODO cell with sextupole and octupole
Tune variation Phase space portrait Massimo Giovannozzi Muon g-2 Meeting - June 12th 2008 14 Novel multi-turn extraction IV Final stage after 20000 turns (about 42 ms for CERN PS) At the septum location Bfield = 0 Bfield 0 Slow (few thousand turns) bump first (closed distortion of the periodic orbit) Fast (less than one turn) bump afterwards (closed distortion of
periodic orbit) About 6 cm in physical space Courtesy Courtesy S. S. Gilardoni Gilardoni Massimo Giovannozzi Muon g-2 Meeting - June 12th 2008 15 No 10: Collisions with large Piwinski angle, and possibly with longitudinally flat bunches. Contact: F. Zimmermann Experiment: Measure beam lifetime and background rates as a function of crossing angle, as a function of bunch length, and as a function of longitudinal profile (Gaussian-like and flat - plus of course the production of bunches with these profiles), possibly also for different synchrotron tunes. The beam-beam tune shift for each measurements must also be known or computed. Questions: This is very likely a demanding task and it remains to be seen if one can change crossing angle and bunch length and vary from Gaussian to flat.
Impressive if one could do that at the Tevatron! 7/28/2010 Cern List of Experiments: F. Schmidt 16 Milestones CERNs general interest has been expressed at the: Tevatron Accelerator Studies Workshop in January 2010. Steve Myers has send an official request for such Tevatron experiments at the end of RUN II to the Fermilab management. At CERN the original list of experiments have been discussed with the experts. For all experiment an outline has been formulated. This meeting will decide if CERNs request will be generally accepted.
For a number of studies a collaboration has already been started with Fermilab. For all other experiments we have to assign a team of experts of both laboratories to discuss the feasibility to do them at the Tevatron. The necessary R&D and preparation of the Tevatron has to be discussed for these studies. I propose that we will not be too rigid and allow for flexibility to add, drop and/or reformulate certain experiments as we go! At the end of 2011 CERN will send the relevant experts for participation in the experiments, which most likely will fit well with the end of the first LHC run. 10 Experiments will on average require 3 shifts. Therefore a total of 2 weeks of experimental time for CERN spread over a total of 6 weeks of studies seems reasonable. 7/28/2010
Cern List of Experiments: F. Schmidt 17 Reserve 7/28/2010 Cern List of Experiments: F. Schmidt 18 7/28/2010 Cern List of Experiments: F. Schmidt 19 7/28/2010 Cern List of Experiments: F. Schmidt 20 7/28/2010
Cern List of Experiments: F. Schmidt 21 AC Dipole Study 7/28/2010 Cern List of Experiments: F. Schmidt 22
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