Some follow-ups

1. Some follow-ups • Convention on the use of the parameters “on_x” • Update table for pre-collision separation and collision crossing angle values • Changes in “as-designed” and proposal for an “as-built” MAD-X sequence. M. Giovannozzi Acknowledgements: H. Burkhardt, S. Fartoukh, J. Jowett, W. Herr, P. Le Roux, T. Risselada, F. Schmidt LHC Beam Commissioning - MG

2. Convention on the use of the parameters “on_x” - I • Three switches are used in the set-up of the optics settings: • on_x*: crossing angle. • on_sep*: parallel separation • on_lhcb, on_alice: spectrometer magnets in IR2/8 • So far, the value 1 of the switch provided the nominal value of the corresponding physical quantity. We would like to keep this philosophy. • Some remarks: • The physical parameters can be re-scaled by setting the switch to an appropriate value. LHC Beam Commissioning - MG

3. Convention on the use of the parameters “on_x” - II • Some remarks: • Scaling with energy can be applied: • Parallel separation: the scaling can be applied to any insertion. • Crossing angle: the scaling can be applied to IR1/5, only. In IR2/8 the presence of the spectrometer breaks the scaling. • During the squeeze: • An appropriate crossing scheme is provided (the parallel separation remains constant). The aim is to vary the crossing smoothly (to the nominal value, e.g. for IR1/5 142.5 mrad). • What to do in case the squeeze is stopped at an intermediate beta* value? LHC Beam Commissioning - MG

4. Convention on the use of the parameters “on_x” - III • Proposal: • An appropriate crossing scheme is provided: this could be selected with a new flag on_coll. • In general: we cannot hope to cover all possible configurations. Knobs should be generated to change easily the crossing scheme in operation. LHC Beam Commissioning - MG

5. Update table for pre-collision separation and collision crossing angle values • Separation: • Standard value of 0.5 mm (half separation) re-scaled with energy • Crossing angles: values provided in Chamonix (W. Herr) and in the table by M. Ferro-Luzzi seems ok. Possible refinement in discussion. For IR8 (reviewed by W. Herr): Crossing angles compatible with both 5 TeV and 4 TeV. LHC Beam Commissioning - MG

6. Changes in LHC sequence - I • Revision launched by Olav Berrig: • Equipment owned by RF Group is declared as RF cavity (even transverse damper…) • Proposal • Define two new elements (this requires changes in MAD-X, active in the next release): • TKICKER (transverse kicker): same as KICKER, but it is not used for closed orbit correction. • PLACEHOLDER: same as INSTRUMENT, but generic. • Then the following changes will be performed: • DFBs: will be defined as PLACEHOLDER (currently are RCOLLIMATORS) LHC Beam Commissioning - MG

7. Changes in LHC sequence - II • APWL, BCTDC, BCTFR, BPLH, BPLV, BPLX, BPTX, BQSH, BQSV, BSRTA, BSRTM, BWS: will be defined as INSTRUMENT (currently are MONITORS). This will avoid using them in closed orbit correction. • XRPH, XRPV: will be defined as RCOLLIMATORS . • X1FCL, X1FCR, X1ZDC001, X2ZDC001, X2ZDC002, X5ZDC001, X5ZDC002: will be defined as INSTRUMENT (currently are ECOLLIMATORS). These elements are not in beam! • MU, ADTKH, ADTKV, MKQA, BQKH, BQKV: will be defined as TKICKER. LHC Beam Commissioning - MG

8. Proposal for the “as-built” LHC sequence • It is not possible to maintain two independent LHC sequences in the layout database. Hence we will have an “as-designed” sequence (frozen) and an “as-built” one (updated according to NCs). • Three classes of NCs are relevant for MAD-X sequence: • Non-working magnet. • Magnet installed in wrong slot (e.g. repair sector 3-4) • Magnets with non-nominal performance (e.g. weak MQTLs in IR3/6/7). • In case of 1. and 2. the corresponding MAD-X elements should be represented with PLACEHOLDER. • In case of 3. the variables Imax and Kmax should be changed in the sequence. LHC Beam Commissioning - MG