NLC 2001 Beam Delivery Layout Tom Markiewicz Fermilab Meeting of Detector WG Leaders 05 January 2001

Summer 2000 Configuration

Summer 2000 Configuration Linacs point at each other One <= 1 TeV Collimation section common to two IRs Energy collimation with tune-up dumps “Relaxed” Betatron collimation with consumable spoilers +10 and –10 mrad Big Bends to get to each of two symmetric IRs 20 mrad crossing angle at each IP Working assumption is “Large” and “Small” detector Non-simultaneous delivery of beam to either detector 280m IP Stretch provides separation and vibration isolation of IR halls New FF with L*=4.3m and magnet apertures designed for 1 TeV Most magnets could be re-used up to 1.5 TeV Length of FF tunnels compatible with 5 TeV Either: same FF lattice to each IR or leave tunnel to IR2 empty (Lehman cost estimate)

Conceptual Problems with Symmetric Two IR Layout Experimenters seem to want full luminosity at 90 GeV – 1 TeV, be able to “quickly” change energy and continually question the maximum energy reach of NLC X-band technology “Big Bend” (designed for 1.5 TeV) limits upper range of energy for HE IR Emittance growth due to SR ~ 5% by limiting strength of bends Magnet apertures set by lowest energy Magnet design set by aperture and highest energy Ambiguous physics justification for two detectors given symmetric layout and fact that only one detector gets data at a time As FF gets shorter, two FF tunnels merge into one lateral displacement of IRs shrinks (44m in ZDR, 16m in CD4) No design provision for gg, which needs larger crossing angle

Base Element of 2001 Layout Emin, Enom, Emax = 250 GeV(?), 500 GeV, 1000 GeV No Big Bend New FF w/ L* = 4.3 m Collimation lattice with dog-leg energy collimation 20 mrad crossing angle One IR Hall with One Large Detector

The 2nd IR Hall in the 2001 Layout Assume a 2nd IR is part of the baseline package Questions: In order of importance Emin, Enom, and Emax for “high luminosity” running Sequential or simultaneous beam delivery Crossing angle, hall size, and facilities infrastructure Detector staging & spacing of halls for vibration isolation Optimal tunnel layout for cost, flexibility, performance? IR2 ??m IR1 Linac and bypass One collimation system or two?

First “Working” Answers to IR2 Questions Transverse and longitudinal spacing of halls for vibration isolation Dx=100m Dz = 0m Emin, Enom, and Emax for “high luminosity” beam delivery 90, 250, 500 GeV, respectively Need to know Emax to before bend tunnels are dug Sequential or simultaneous beam delivery Sequential BUT supporting simultaneous operation if issues resolved Polarized beam to each IR 2nd INDEPENDENT collimation system allows possibility of simultaneous operation at different energies Crossing angle, hall size, and facilities infrastructure 30 mrad (20-40 possible; keep E(L*Bsq)5/2 < current value) 10mrad gg stay-free requires bigger angle 2nd detector? Precision?

Site Layout Dx=100m Dz = 0m

BDIR Detail: Dx=100m Dz = 0m FF2 27mrad Coll2+Bends 52mrad Coll1 FF1

An Alternative Layout Length of tunnels to IR#2 is just that required for bends that maintain good emittance beam at 500 GeV c.o.m. 110m of tunnel per 10mrad of bend for 5% dilution if Emax=500 GeV Can we reduce IR separation and either reduce cost or increase program flexibility? Reduce Dx to ~25m Vibration, simultaneous occupation of halls, etc?? Use ONE collimation system for BOTH IRs Need some “empty” IP-Stretch tunnel to make geometry work Second collimation system in same tunnel also allows possibility of simultaneous operation at different energies 25 mrad big bend and NO reverse bend Are there advantages to ONE big IR Hall?

Site Layout Dx=25m Dz = 0m One Collimation Tunnel per Side FF2 0 mrad Coll Bend 25mrad Stretch FF1

Reversed Linac Angle, IR Separation = 25m and Separate Collimation Lattices and IR lead to Big Bend + Reverse Bend Angles ~ 21.8mrad

Another Possibility: Dx=25m Dz = 440m One Collimation Tunnel per Side FF2 0 mrad Coll Bend 25mrad Stretch FF1

Site layout with Dx=25m Dz = 440m

VERY, VERY Rough Cost Estimate Length Scaling Only, NOT Parts counting

Summary It’s really a “User’s choice”: You get what you pay for Model 0: One IR Cheapest option: 251M$ Model 1: Dx=100m Dz = 0m Most flexible? Most bending, perhaps lowest maximum energy reach Most expensive: 499M$ Model 2: Dx=25m Dz = 0m Allows for flexibility in detector/IR staging. Is this interesting? 407M$ plus 60M$ for second collimation system (simultaneous running) Model 3: Dx=25m Dz = 440m Seems best suited to a low start up cost Begin with one collimation system & sequential data taking Better vibration isolation; same cost as Model 2 Is there another variation we are missing?

Conceptual Problems with Symmetric Two IR Layout Experimenters seem to want full luminosity at 90 GeV – 1 TeV, be able to “quickly” change energy and continually question the maximum energy reach of NLC X-band technology “Big Bend” (designed for 1.5 TeV) limits upper range of energy for HE IR Emittance growth due to SR ~ 5% by limiting strength of bends 330m for 10mrad of bend at 750 GeV/beam Length of Big Bend scales as E_max for constant De For fixed geometry, emittance scales as E6; Luminosity as g-2.5 Magnet apertures set by lowest energy Given aperture, once max beam divergence is reached, since emittance scales as 1/E, need to scale beta function by 1/E Hard to meet PS sensitivity requirements (~10-5) without limiting range Ambiguous physics justification for two detectors given symmetric layout and fact that only one detector gets data at a time As FF gets shorter, two FF tunnels merge into one lateral displacement of IRs shrinks (44m in ZDR, 16m in CD4) No design provision for gg, which needs larger crossing angle

Luminosity Scaling with Energy Assuming same injector, the luminosity scales as: Luminosity in high energy FF scales linearly with energy between 250 and 1 TeV Low energy FF scales similarly but at lower energy!

Reversed Linac Angle Leads to Larger Bend and Reverse Bend to IR2 When IR Separation = 100m

Reverse Linac Angle and Common Use of Collimation Lattice when IR Separation is 25m leads to Bend and Reverse Bend Tunnel Angles Too Large to be Supported by Tunnel Length

Separate collimation systems & standard linac angle

Another Possibility: Dx=25m Dz = 300m

How About: Dx=25m Dz = 500m