# Presentation: 460031

## Future Facilities for Hadron Collider Physics

- Tevatron -> LHC
- LHC-ology
- SLHC
- DLHC
- VLHC
- Machine Detector Interface
- Enabling Technology
- (Linear colliders SRF, Hadron colliders SC magnets)
- Summary

## Tevatron -> LHC

- The LHC (the first of the next hadron colliders)
- ‘Conventional’ Hadron Collider technology (NbTi magnets at 2K, SRF) and design - no problem
- Energy
- 7 Tev = 7 * Tevatron
- 27 km = 4 * Tevatron
- 8.3 T field = 2 * Tevatron
- Luminosity
- 1034 = 60 * Tevatron (an issue but in principle a good one)
- Beam Power (a function of energy and luminosity)
- 350 MJ = 250 * Tevatron (a real issue !!! )

## Tevatron -> LHC

- The LHC is the R&D Project for the future: it has all of the problems of the future hadron machines (as we currently understand them)
- Stored energy -> component damage
- Beam loss sensitivity -> quench problems, ‘operability’
- Luminosity/Energy -> IR debris -> radiation damage, heat loads
- Beam current/Energy -> synchrotron radiation -> vacuum issues

## Tevatron -> LHC

## Tevatron -> LHC

## Tevatron -> LHC

- 350 MJ of circulating beam energy: magnets will quench with mJ of deposited energy (11 orders of magnitude)
- Problems involve limiting initial beam loss to 1 part in 105 with complex beam dynamics, alignment(absolute, relative, and dynamic) of many (~60) elements at fractions of a sigma, collimator damage, collimator impedance, amplifies the impact of any beam instability
- R&D: in principle the basic mechanisms are known and can be simulated.  Machine design includes two cleaning insertions.  To date there is no robust system for the design luminosity.

## Tevatron -> LHC:  physics of the beam pipe vacuum

- The LHC will start to experience synchrotron radiation effects in a hadron machine for the first time (Edep ~200mW/m).  Electron cloud build up induced by synchrotron radiation results in a vacuum increase which in turn leads to cryogenic loads (at best), or beam instabilities (at worst).
- R&D: many years of measurements at light sources and the SPS together with detailed simulations has resulted in a situation which appears to be well understood.  Operating scenarios involving lower luminosity scrubbing cycles.

## SLHC - Super LHC

- 1034 -> 1035 ‘the ultimate luminosity’
- (kW of beam power from each side of the IP)
- Ignoring everything I just said about stored energy and vacuum problems !  1035 is achieved by:
- Increase the bunch intensity ~ 50%
- Double the number of bunches
- Increase focusing strength at the IP to reduce spot size
- Must reduce long range beam-beam interaction
-  increase crossing angle to 0.3 mrad -> 0.6 mrad or more
- Separate beams earlier

## SLHC - possible IR modifications

- There are several potential ways to increase the crossing angle

- All of these schemes have in common the requirement for large aperture high gradient quadrupoles and/or very high field dipoles
- Standard LHC magnet technology (NbTi at 2K) does not make it
- Thus the SLHC requires next generation magnet technology => Nb3Sn

- 30 long range interactions

- 12 long range interactions

## SLHC - Nb3Sn Magnet Development

- Nb3Sn is a difficult material to work with when in its SC form:
- Brittle
- Strain sensitive
- Easily damaged
- This technology development is one of the main goals of the US LARP Program (Fermilab, LBL, BNL)

## SLHC - Nb3Sn Magnet Development - Wind-and-React

- Test coils from LBL for the LARP program

## SLHC - Nb3Sn Magnet Development - React-and-Wind

- The is obviously a device with “issues” but it did reach the estimated short sample limit.  A proof of principle.

## SLHC - (fast-track) Schedule

- Select first choice scheme for the upgrade at a CARE-HHH meeting in Valencia in October of this year
- Demonstration of prototype quadrupole 2009 (LARP)
- Finalize upgrade design 2010
- IR magnet pre-production 2011
- IR magnet production starts 2012
- LHC IR replacement 2015

## DLHC - LHC Energy Doubler (or more)

- Increase dipole field from 8T to 16T (or beyond) gives 25 TeV collision energy
- As one can imagine there are a host of issues:
- New Injector (replace SPS with rapid cycling SC ring ?)
- Stored Energy ~ 1-2 GJ
- Cryogenic capacity
- IR design
- In the spirit of this gathering I will ignore these minor issues and look at the fundamental ones :
- 16T dipoles (about as high as one can go with Nb3Sn)
- the vacuum problem (several W/m line density, 150kW total power)

## DLHC - High Field Dipole R&D

- Design Features
-   Block-coil supported by yoke and shell
-   Simple and cost-effective configuration
-   Flat cables, double pancake coils
-   Separation of high field/high stress  	points
-   Bladder & key assembly

- Dipole HD1 from the LBL magnet program.
- Very small aperture (not an accelerator magnet) but demonstrates high coil stresses and pre-load.  Nominal field ~ 16T

## DLHC - High Field Dipole R&D

- The magnet performance is deemed encouraging

## DLHC - Vacuum Issues

- > 100kW of synchrotron beam power is excessive in terms of a cryogenic load even if it is onto a 10K beam screen

- Unproven, no real R&D

## VLHC - The Ultimate Hadron Collider ?

- After the Snowmass 01 meeting there are several versions of the VLHC.  Generally we seem to be talking about:
- ~ 50 Tev beam energy
- > 1034 luminosity
- Details of the other machine parameters will (presumably) reflect the final technology and design choices.
- My favourite:
- ~ 100 Tev collision energy
- ~ 100 Km circumference => 12T dipole field
- New Dynamical regime for proton colliders
- Synchrotron radiation damping at very high proton beam energies can result in hitherto unobtainable beam densities which may prove to be very beneficial in achieving machine performance goals.
- Radiated power will inevitably complicate the beam tube environment.
- Is there an appropriate balance at these energies ?

## VLHC - Store evolution

- Maximum Luminosity with minimum number of protons
- Equilibrium emittance independent of initial emittance.  Eases specifications on injector chain
- Vertical emittance assumed to be 10% of the horizontal
- Emittances determined by beam heating not equilibrium values

## VLHC- Issues

- Beam Power
- 2 GJ - enough said, though a better behaved 2 GJ than the LHC upgrade
- IP debris - many kilowatts of power into the final focus magnetic elements
- Vacuum effects
- Radiated power in the  5-10 W/m range.  This is not well understood at present but in principle there is sufficient pumping speed in a beam screen environment to maintain an acceptable vacuum.   Note higher magnet fields imply lower beam energy if power is fixed.
- Total Radiated Power: In addition to local power there is also ~ 0.5 MW of total power into the beam screen.  Probably requires photon stops to intercept power at higher temperatures.
- Ring Size:
- Sensitivity to dynamic effects in magnets : many magnets
- Technical feasibility of the machine would not appear to be as big of an issue as other methods to achieve these collision energies

## Machine Detector Interface

- All trends in the machine are in the direction of making life (more) difficult for the detectors.
- High luminosities lead to more events/X-ing (LHC nominal  19.2, SLHC ~100).  The machine would prefer less bunches (reduce long range beam-beam) rather than more which doesn’t help.
- High luminosities lead to significant radiation damage arising from the collisions themselves.  At 10E35 there is 9KW of beam power emanating from each side of the IP
- Large stored beam currents result in increased beam halo
- Synchrotron radiation will degrade the vacuum giving more background rates from beam-gas
- Detectors will need to be more robust with respect to many sources of background

- CDF Top event

- ATLAS Au-Au

## Enabling Technology

- The LHC is big, technically complex, operationally twitchy and expensive
- We would like simple, robust and cheap
- So what happened ?
- We are victims of our own success.  In the last 50 years we have gone from 1.5T (SPS), 4T (Tevatron), 8T (LHC): from warm to cold to very cold, 10mK temperature uniformity, 60 micron relative alignment across kilometers, 350 MJ, 10-5 stability in many systems, etc...
- It’s getting too hard to be cheap and simple

- Too complex

## Enabling Technology:  The performance of very cold technology with the simplicity of warm - the lure of high temperature superconductivity.

- Capable of high fields
- Minimal sensitivity to radiation and radiation resistant
- Minimal sensitivity to temperature variations
- Higher operating temperatures feasible i.e. simplified cryogenic systems

## Enabling Technology:  the lure of high temperature superconductivity (continued)

- But HTS is very expensive, brittle and lacks sufficient currents carrying capacity
- Do we care how expensive it is ?	Well yes actually we do
- Superconductor costs		NbTi	$1.0 /kA-m at 5T
- 				Nb3Sn	$4.75 /kA-m at 12 T
- 				Bi-2223	~$30 /kA-m
- LHC dipoles:	superconductor 	300 MCHF
- 			other materials	200 MCHF
- 			other magnetic items	50 MCHF
- 			assembly labour	500 MCHF
- American Superconductor is starting to introduce 2nd generation HTS tape (BSCCO -> YBCO) claiming that their main goal is to lower the cost.  We need a cost/performance gain of ~10.
- HEP will not drive this market and our desirable conductor characteristics tend to be a little different from the commercial world - we both care about money though.

## Enabling Technology:  the lure of high temperature superconductivity (continued)

- So where do we go next ?
- Probably the next step is to demonstrate feasibility in some “boutique” application that isn’t too cost sensitive or where HTS provides some unique benefit.
- Dramatically increasing power costs for the labs could prove to be a help in this regard.  There is some interest in replacement systems for copper and iron magnets in such applications as light sources, neutrino beamlines, ILC extraction lines where the principle benefit is energy efficiency.
- Keep an eye on the power distribution industry as a technology driver

- HTS magnet R&D for RIA (nuclear physics) - proof of principle

## Summary

- Hadron Colliders can achieve the highest energies and will for the foreseeable future
- The LHC is an excellent R&D project for the future
- LHC upgrades are hard but improvements are always possible.  People are actively thinking about such scenarios.
- We can contemplate one more generation of machines after the LHC with known techniques.
- High Temperature Superconductors have many desirable features for a Hadron Collider but we still need a significant improvement in cost/performance to approach viability

- An excellent R&D Project