1. DA Studies with crossing angles and higher order corrections
Emilia Cruz
On behalf of the JAI FCC Team
April 4th, 2017

2. Status after last meeting
Solved problems:
Sixtrack problems with thick lattice, runs ok with thin lattice.
DA studies performed with crossing angles, errors, on and off momentum.
Installation of non-linear correctors gave encouraging results increasing the DA.
Unsolved problems
DA for off-momentum studies without non-linear correctors is zero.

3. Previous Results On_momentum Off_momentum Correction On_momentum
Min DA
Off_momentum
None
6.4σ 0σ
b3/a3
7.9σ 4σ
b3/a3/b4/a4
8.5σ
6.8σ
b3/a3/b4/a4/a6
39.7σ
6.9σ

4. Previous Studies – Look for origin
Looking into 0 DA
Previous Studies – Look for origin
Only fails for 4 seeds. No obvious difference between W functions, hpq terms or magnetic field configuration for these seeds.
Look into comparison errors between FCC and HLLHC. Similar RDT’s.
Beta-beating significantly larger for one of the bad seeds.

5. Previous Studies – Look for origin
Looking into 0 DA
Previous Studies – Look for origin
Only fails for 4 seeds. No obvious difference between W functions, hpq terms or magnetic field configuration for these seeds.
Look into comparison errors between FCC and HLLHC. Similar RDT’s.
Beta-beating significantly larger for one of the bad seeds.
Current Studies – Work in correction scripts
Optimize cor_spur_flexible with optics matching (Antoine’s version)
Optimize chromaticity correction, work with sextupole families.

6. Examine Beta beating Examine cor_spur_flexible.
A. Chance.
FCC-hh General Meeting
16/09/16
Examine cor_spur_flexible.
Correct minor details in matching variables.
Current version of the correction includes 2 parts: Dispersion matching and optics matching. Add second part to the new version with errors.
Start on IPL
Match dispersion in IPA
Start on IPA
Match dispersion in IPB
Start on IPL
Match dispersion in IPA
Start on IPL
Match optics in IPA
Control β in quads
Start on IPA
Match dispersion in IPB
Start on IPA
Match optics in IPB
Control β in quads

7. Examine Beta beating Examine cor_spur_flexible.
A. Chance.
FCC-hh General Meeting
16/09/16
Examine cor_spur_flexible.
Correct minor details in matching variables.
Current version of the correction includes 2 parts: Dispersion matching and optics matching. Add second part to the new version with errors.
After several iterations with the matching procedure best result gave positive minimum DA with a value of 1.4σ
Start on IPL
Match dispersion in IPA
Start on IPA
Match dispersion in IPB
Start on IPL
Match dispersion in IPA
Start on IPL
Match optics in IPA
Control β in quads
Start on IPA
Match dispersion in IPB
Start on IPA
Match optics in IPB
Control β in quads

8. Orbit Deviation
Cor_spur_flexible creates orbit deviation around IRA and IRG. In particular around IRG this deviation is larger.
Test if this deviation causes problems in DA, particularly with sextupoles located there.

9. Orbit Deviation
Cor_spur_flexible creates orbit deviation around IRA and IRG. In particular around IRG this deviation is larger.
Test if this deviation causes problems in DA, particularly with sextupoles located there.
Min DA:
1.8 σ
Chromaticity corrected using all sextupoles.

10. Orbit Deviation
Cor_spur_flexible creates orbit deviation around IRA and IRG. In particular around IRG this deviation is larger.
Test if this deviation causes problems in DA, particularly with sextupoles located there.
Min DA:
1.8 σ
1.4 σ
Chromaticity corrected using all sextupoles.
Chromaticity corrected using all sextupoles BUT sextupoles in arcs adjacent to IRA and IRG.

11. Orbit Deviation
Cor_spur_flexible creates orbit deviation around IRA and IRG. In particular around IRG this deviation is larger.
Test if this deviation causes problems in DA, particularly with sextupoles located there.
Min DA:
1.8 σ
1.4 σ
2.1σ
Chromaticity corrected using all sextupoles.
Chromaticity corrected using all sextupoles BUT sextupoles in arcs adjacent to IRA and IRG.
Chromaticity corrected using all sextupoles BUT sextupoles located in y-orbit deviation around IRG.

12. FCC-hh General Meeting
Orbit Deviation
Cor_spur_flexible creates orbit deviation around IRA and IRG. In particular around IRG this deviation is larger.
Test if this deviation causes problems in DA, particularly with sextupoles located there.
Min DA:
1.8 σ
1.4 σ
2.1σ
1.2σ
Chromaticity corrected using all sextupoles.
Chromaticity corrected using all sextupoles BUT sextupoles in arcs adjacent to IRA and IRG.
Chromaticity corrected using all sextupoles BUT sextupoles located in y-orbit deviation around IRG.
Try SSC-like spur like correction. Spurious dispersion corrected without the orbit deviation but problems in strength of skew quads (reported by Antoine).
A. Chance.
FCC-hh General Meeting
22/09/16

13. FCC-hh General Meeting
Orbit Deviation
Cor_spur_flexible creates orbit deviation around IRA and IRG. In particular around IRG this deviation is larger.
Test if this deviation causes problems in DA, particularly with sextupoles located there.
Min DA:
1.8 σ
1.4 σ
2.1σ
1.2σ
Chromaticity corrected using all sextupoles.
Chromaticity corrected using all sextupoles BUT sextupoles in arcs adjacent to IRA and IRG.
Chromaticity corrected using all sextupoles BUT sextupoles located in y-orbit deviation around IRG.
Try SSC-like spur like correction. Spurious dispersion corrected without the orbit deviation but problems in strength of skew quads (reported by Antoine).
A. Chance.
FCC-hh General Meeting
22/09/16

14. New error table
Adjustments to error table (Roman). New error table has about 7% smaller reference radius. How much is the DA affected?
Correction
Old error table
3.7σ
6.3σ
6.8σ
5.5σ
None 0σ
b3/a3 4σ
b3/a3/b4/a4
b3/a3/b4/a4/a6
6.9σ

15. New error table
The DA goes down as expected but results are very similar
Correction
Old error table
New error table
5.5σ
None 0σ
b3/a3 4σ
3.7σ
b3/a3/b4/a4
6.8σ
6.3σ
b3/a3/b4/a4/a6
6.9σ

16. New correction scripts
With the new correction scripts the DA increased by about 2-3σ, particularly important in the case with non-linear correctors.
Correction
Old error table
New error table
+ new corrections
None 0σ
1.9σ
b3/a3 4σ
3.7σ
5.6σ
b3/a3/b4/a4
6.8σ
6.3σ
9.4σ
b3/a3/b4/a4/a6
6.9σ
10.1σ

17. Conclusions and Further work
Previous results gave encouraging results to improve the DA, increasing from 0 minimum DA without non linear correctors to 6.8 σ with a3/b3/a4/b4/b6 correctors.
Changes in the correction scripts resulted in a positive minimum DA for the off-momentum case with non-linear correctors.
The new error table and the new correction scripts were implemented also for jobs with non-linear correctors. The best case scenario for off momentum studies gives 1.9σ with no linear correctors and 10.1σ with a3/b3/a4/b4/b6 correctors.
Continue working with location/length/configuration of the magnets and with the corrections scripts.
Resolve problem with matching the optics in the SSC correction to study if this correction results in an improvement on the minimum DA.
Get back to problem with thick lattices.
Any other suggestion is more than welcome!