# Presentation: 580423

## Brief Summary of the ILC/LET workshop, Daresbury, Jan 8-11 2007

- Paul Lebrun
- Fermilab CD/AMR

- Jan 08 2007

## 3 Meetings, one time, one place.

- Machine Advisory Committee:
- review of the current RDR, just prior to presentation of the ILC cost.
-   I can’t report on this, LET: Low Emittance transport, regular meeting
- EuroTev meeting:
- ILPS/LET, METSTAB,  Diag, DR
- CLIC and ILC...and ATF, ATF2
- ILC/LET: Low Emittance Transport:
- Regular meeting, we try to have face to face meeting at least 2 times a year.
- Participants: ~ 6 U.S., 4 Japan, ~ 15 Europe.. (CERN, DESY, Daresbury..)

- Jan 08 2007

##  Agenda/Programme

- http://ilcagenda.cern.ch/conferenceDisplay.py?confId=1265
**Most of the slides have been uploaded there!   **

- Jan 08 2007

##  LET, by sub machines (I of 3) 

- Ring to Main Linac:
- Three (almost) independent calculations indicate that, in the static limit, given our standard (and not yet really achieved) misalignment errors, projected emittance growth budget is not quite met ( ~ factor 2 too large).
- non-local corrections (“bumps” play a major role)
- PT from SLAC is re-designing the turn-around and the skew correction section(s?)
- Dynamical simulation: only preliminary results, focus was on getting all the correction right..
- Two nagging problems:
- Tolerance on a few Kz stray B filed in long transport: 7.5 nTesla !
- Steering through the Bunch Compressor, without being able to change the momentum “significantly”

- Jan 08 2007

##  LET, by sub machines (2 of 3) 

- 	Main Linac
- Curved Lattice, with  constraints from cryo-subsytem.
-  In the static limit, starting from 15 GeV/c, with “bumps”, emittance growth is only a few nm.Rad, within budget, or negligible.
- Progress on simulation of the undulator, results encouraging, but a bit more work on accurate:
- description of the inductive wakes is needed (beam pipe is only 7.5 mm diameter ).
-  simulation of synchrotron radiation.
- Dispersion Correction section at the end, is it Main Linac or BDS ( nobody seems to have room for it!)
- Dynamical simulation: simple algorithms for post-steering, feedback corrections seems to do the trick.

- Jan 08 2007

##  LET, by sub machines (3 of 3) 

- 	Beam Delivery System (BDS)
- Mature 14 mRad x-angle design, with one I.P.
- Contentious revival of the zero-degree X-angle... Need very good separators! Nice but risky.
- Thorough static steering simulations to optimize luminosity of the IP show that this design meet the spec...
-  Realistic Dynamical simulation, along with *all* upstream defects remains to be done.
- Such dynamical simulation will take a lot of CPU!.

- Jan 08 2007

##  LET, Algorithms & Tricks 

- 	Bumps
- Post Dispersion Free Steering.
- Final, last (?) static correction.
- non-local ( pre or post-correcting, km away from the where the problem really occurred.)
- Not yet ( I think..) really proven in complicate dynamical cases.
**Getting the right Knobs**
- Using Singular Value Decomposition analysis, one can find the “right” i.e., nearly orthogonal and ordered by importance of eigenvalues, combination of correctors or cavity movers (CLIC context) to greatly simplify the static steering process.

- Jan 08 2007

##  LET, Benchmarking  

- 	Five LET codes have been carefully benchmark on the old Tesla Main Linac lattice, and found to agree relatively well (few percent the projected emittance growth)  The 6th one, CHEF seems to “stand out” compared to the others.
- 	Perhaps implying that CHEF is not quite adequate for LET code ..
- 	Difference between CHEF and Merlin will be studied and documented. Some difference are relatively trivial, like the exact definition of projected emittance. Others are more time consuming to unveil, because, Merlin, like MatLIAR/Lucretia is “optical” i.e., propagating rays, say, Py/Pz while CHEF is “6D canonical”, propagating Py/Pref. .. All equations differs!
- 	Tedious work, but needed: need to find out to what extend non-linearities matter: is LET “very linear”, intrinsically or it is because the code don’t bother to implement some of these non-linearities?

- Jan 08 2007

##  30 seconds Summary:   

- 	Driving on the wrong side of the road is fun, and (relatively) safe.
- 	Queen’Anne Head, in Frodscham, Pub is O.K, English beer drinkable.  Food (relatively) cheap.
- 	Winter in North Wales, England, is beautiful, just like my native country!
- 	Next meeting:  LCWS 2007
- 	Hamburg, Germany30 May - 4 June 2007

- Jan 08 2007

## On Benchmarks/Checks

- CHEF vs Merlin tracking,
-    on “Benchmark 2”
-    Quadrupoles kicks due to displacement
-   Short Range Wakes
-    Cavity tilts...
-   Spike at 800 m. in projected emittance has a bigger amplitude (other codes saw similar features).

- Jan 08 2007

## On Benchmarks/Checks

- Local Dispersion can be slightly off, yet, once corrected for dispersion,
- better agreement.
- Detailed agreement, after empirically finding out the rotation axis intercept for cavities..

- Jan 08 2007