1 O. Napoly ECFA-DESY Amsterdam, April 2003 Machine – Detector Interface : what is new since the TDR ? O. Napoly CEA/Saclay

2 O. Napoly ECFA-DESY Amsterdam, April 2003 Outline  New final focus with l* = 5 m  BDSIM Background Simulation Code  Open problem of the extraction line

3 O. Napoly ECFA-DESY Amsterdam, April 2003 New final focus with l* = 5 m s  Energy spread  chromatic aberrations   Final doublet:

4 O. Napoly ECFA-DESY Amsterdam, April 2003 K+K+ K-K- s   X-X-  X+X+  X-X-  X+X+ Sextupole in the doublet  local chromatic correction Chromatic Correction ‘à la NLC’ Final doublet :

5 O. Napoly ECFA-DESY Amsterdam, April 2003 New Final Focus ‘à la NLC’ l* IP waist β* Smaller l*  smaller β*  smaller spot size BUT σ y * is limited by beamstrahlung Better chromaticity correction  larger l* Chromaticity : ξ = l* / β*

6 O. Napoly ECFA-DESY Amsterdam, April Final doublets moved out of the solenoid (9m, 4T) 2.Tungsten mask 2 m shorter  easier cantilever support New Final Focus with l* = 5m TDR doublet l*=3m Advantages from the machine point-of-view

7 O. Napoly ECFA-DESY Amsterdam, April 2003 New Final Focus with l* = 5m Advantages from the detector point-of-view (see A. Stahl)  Larger forward acceptance at low angles  Final doublets moved out of the calorimeters  less e.m. showers in the detector

8 O. Napoly ECFA-DESY Amsterdam, April 2003 NLC type correction, l* =5m SF1, SD1 SF2 SD2 SF3 Beamstrahlung Dump IP angular dispersion D’ x * = 10 mrad

9 O. Napoly ECFA-DESY Amsterdam, April 2003 Correction type NLC, l* =5m IP spot sizes and luminosity L/L 0 = 0.86 for  E /E = 0.4 %,

10 O. Napoly ECFA-DESY Amsterdam, April 2003 Optics Summary The ideal solution is surrounded, but not yet found

11 O. Napoly ECFA-DESY Amsterdam, April 2003 Comparison of outgoing doublet acceptances for l* = 3,4,5 m Differences are small. Tracking simulations are needed l*=5m acceptance : better for lower energies worse for high energies

12 O. Napoly ECFA-DESY Amsterdam, April 2003 Synchrotron Radiation Extraction Collimation requirements for l* = 5m Φ = 48 mm inner mask s = 4 m Φ = 24 mm

13 O. Napoly ECFA-DESY Amsterdam, April 2003 Collimation Requirements l* [m] s mask [m] NxNy TDR New FF New FF  new collimation section required with tail folding by octupoles

14 O. Napoly ECFA-DESY Amsterdam, April 2003 BDSIM Background Simulation MAD to GEANT translator was needed to update background simulations w.r.t. new BDS optics BDSIM (G. Blair) simulates beam transport and collimation efficiency energy deposition from halo particles synchrotron radiation muon production and transport to the IP beam-gas interaction and transport to the IP neutrons production and transport (?)

15 O. Napoly ECFA-DESY Amsterdam, April 2003 BDSIM Geant4 BDS Simulation Program Include material interations together with machine-style tracking

16 O. Napoly ECFA-DESY Amsterdam, April 2003 Halo Energy loss along BDS (no SR included)

17 O. Napoly ECFA-DESY Amsterdam, April 2003 Collimation Efficiency Collimation inefficiency

18 O. Napoly ECFA-DESY Amsterdam, April 2003 Muons Trajectories Most of the muons come from the energy collimator

19 O. Napoly ECFA-DESY Amsterdam, April 2003 Beam-Gas Interactions

20 O. Napoly ECFA-DESY Amsterdam, April The Extraction Line Problem Incoming Beam Outgoing Beam Beamstrahlung

21 O. Napoly ECFA-DESY Amsterdam, April 2003 New parameters Vertical angular spread Shadow: Distance from IP: 45 m 2 m long 5 mm thick 7 mm vertical distance from nominal beam (~156 µrad) Copper Septum Blade: Distance from IP: 47 m 16 m long 5 mm thick ~7 mm vertical distance from nominal beam Copper Septum

22 O. Napoly ECFA-DESY Amsterdam, April 2003 Realistic Beam Shadow: Average deposited power: ~15 kW Septum blade: Average deposited power: ~80 W

23 O. Napoly ECFA-DESY Amsterdam, April 2003 Questions Meeting on December 3rd 2002 identified the following questions: – Septum Magnet Design Failure modes What power can the thin blade cope with ? – Reliability of electro-static separators IR is a highly charged environment – Power loss from the charged particle extraction ? – Is a (small or large) crossing angle a solution ? – 800 GeV upgrade

24 O. Napoly ECFA-DESY Amsterdam, April 2003 Crossing Angle Solution The trade-offs are, from the machine perspective Pros extraction line diagnostics easier (if feasible at all) Cons final doublets technically difficult (permanent quads) tuning of crab-crossing cavities

25 O. Napoly ECFA-DESY Amsterdam, April 2003 Conclusion Help is badly needed !