# Presentation: 533347

## Proton Driver II Design Study

- FNAL Directorate has initiated PD2 Design Study
- Goal is 5x more protons in Main Injector.
- Side-by-side studies *(including cost)* of:
- Optimized 8 GeV Booster Synchrotron
- 8 GeV Superconducting Linac
- Main Injector modifications for increased beam current
*This is mainly a technical talk on the 8 GeV Linac.*

- 15 Jan 2002

## 8 GeV Injector Linac Concept

-  1) Copy SNS Linac design up to 1.3 GeV
- 	*(Reduced beam current and relaxed schedule allow some design optimizations)*
-  2) Use  “TESLA”  Cryomodules  from  1.3  8 GeV
-  3) H- Injection at 8 GeV in Main Injector
-   “Super-Beams” in Fermilab Main Injector:
*	**2 MW Beam power, small emittances, and minimum (1.5 sec) cycle time*
- Other possible missions for unused linac cycles:
- 8 GeV  program, 8 GeV electrons ==> XFEL, etc.

- 15 Jan 2002

## 8 GeV Injector Linac - Possible Sitings

- 15 Jan 2002

## 8 GeV Linac Parameters

- 15 Jan 2002

## Benefits of 8 GeV Injector

- Benefits to  and Fixed-Target program
- solves proton economics problem:  > 5E18 Protons/hr at 8 GeV
- operate MI with small emittances, high currents, and low losses
- Benefits to Linear Collider R&D
- 1.5% scale demonstration of TESLA economics
- Evades the Linear Collider R & D funding cap
- Simplifies the Linear Collider technology choice
- Establishes stronger US position in LC technology
- Benefits to Muon Collider / ****-Factory R&D
- Establishes cost basis for P-driver and muon acceleration
- Benefits to VLHC: small emittances, high Luminosity
- ~4x lower beam current reduces stored energy in beam
- Stage 1: reduces instabilities, allows small beam pipes
- Stage 2: injection at final synchrotron-damped emittances

- 15 Jan 2002

## Main Injector with 8 GeV Linac

- 1.5 Second Cycle time to 120 GeV
- filling time 1 msec or less
- no delay for multiple Booster Batches
- no beam gaps  for “Booster Batches” -- only Abort gap
- H- stripping injection at 8 GeV
- 25 mA linac beam current
- 90-turn Injection gives MI Beam Current  ~2.3 A
*( SNS has 1060 turn injection at 1 GeV )*
- preserve linac emittances ~0.5 (95%) at low currents
- phase space painting needed at high currents
*   **** **can put a frightening amount of beam in MI*

- 15 Jan 2002

## 120 GeV Main Injector Cycle with 8 GeV Synchrotron

- 15 Jan 2002

## 120 GeV Main Injector Cycle with 8 GeV Linac, e- and P

- 15 Jan 2002

## 8 GeV Linac Allows Reduced MI Beam Energy without Compromising Beam Power

- MI cycles to 40 GeV at 2Hz, retains 2 MW MI beam power

- 15 Jan 2002

## Running at Reduced Proton Energy Produces a Cleaner Neutrino Spectrum

- Running at 40 GeV reduces tail at higher neutrino energies.
- Same number of events for same beam power.
*(Plot courtesy Fritz & Debbie)*

- 15 Jan 2002

## Very Rough Cost Estimates

- 1)  Scaled from TESLA costs
- 2)  Scaled from SNS actual costs
- 3) First stab at bottom-up cost est.
- use SNS actual costs where reasonable
- independent, bottom-up cost estimates elsewhere
*Not yet completed but this is the way to go.*

- 15 Jan 2002

## Rough Cost, Scaled from TESLA

- TESLA Project Cost (European)	          $3B
- subtract damping rings, IR, Injector	       $2.5B
- US Cost Basis (x2) for bare linac	          $5B
- Scale to 7 GeV    (7/500) = 1.4%	       $70M
- TESLA quantity Discount (7/500)-0.074 =1.37     $100M
- Include Fixed Project Cost  ($50M??)   **$150M**

- 15 Jan 2002

## Rough Cost, Scaled from SNS

- SNS Project Cost				$1300M
- SC Linac Cost	 (approx, incl. civil)	  $250M
- Scale SCRF by energy (7.6/0.8)	       x10
-  	 							**$2.5 B**
*There are many good technical reasons why the TESLA linac should be cheaper.  But how much? *
*We need detailed breakdowns to understand the apparent disconnect between TESLA and SNS cost estimates.*

- 15 Jan 2002

## Bottom-up Cost for 8 GeV -  the game plan:

- Can use SNS _Actual_ Costs for:
- Niobium
- Finished Cavities (industrially produced)
- Klystrons, circulators, and RF couplers
- Civil construction for Linac & associated buildings
- Cryogenics and Cryoplant including civil
- T. Nicol independent cost est. for TESLA style Cryostat, and Assembly
- FNAL Bottom-up Cost Est. for TESLA-Style RF
- MI actual costs for tunnel, Beam Dump, etc.
- FMI for Controls & Project Overhead

- 15 Jan 2002

- 15 Jan 2002

## Civil Construction Costs

- 15 Jan 2002

## Design Optimizations of SNS Linac

- The Spallation Neutron Source (SNS) is a well organized and documented project, and a good model for many aspects of the 8 GeV Linac.
- Design optimizations possible for 8 GeV Injector:
- Lower average beam current and pulse rate (10 Hz vs. 60Hz)
- Higher accelerating gradients can be assumed due to successful SC Cavity R&D by SNS, TJNAF, TESLA, Cornell, KEK, et.al.
- Less schedule pressure allows for additional component development where cost-effective
- 8 GeV Linac can marry the best of TESLA, CEBAF, and SNS system designs

- 15 Jan 2002

## Which Optimizations of SNS are worth it?

**1)  TESLA-style RF fanout**
- drive many (8-12) cavities from single big klystron
- must complete SNS development of fast phase shifter
**2)  Eliminate warm Cavity-Coupled Linac (CCL)**
- Use Beta=0.47, 805 MHz Superconducting cavities developed for RIA project by NSCL/Jlab/INFN
- Similar cryomodules & RF as Beta=0.61, 0.81 cavities
- SNS considered this but dropped due to schedule
**3) Use TESLA-style cryomodules with cold quads**
- longer cryomodules with fewer end costs
**4) Civil construction for fewer klystrons per meter**

- 15 Jan 2002

## Layout of 8 GeV Linac

- Copy SNS Front-end, RFQ, DTL up to 87 MeV
- 805 MHz Superconducting Linac up to 1.3 GeV
- Three sections: Beta = 0.47,  0.61,  0.81
- Use cavity designs developed for SNS & RIA
- TESLA-style cryomodules for higher packing factor
- 1.2 GHz “TESLA” cryomodules from 1-8 GeV
- This section can accelerate electrons as well
- RF from one Klystron fanned out to 12 cavites

- 15 Jan 2002

- 15 Jan 2002

## Linac:  0 - 87 MeV

- Direct Copy of SNS Design:
- Ion Source
- RF Quadrupole (RFQ)
- Low-Energy Beam Transport (buncher & chopper)
- Drift Tube Linac (402.5 MHz Normal Conducting)
*SNS work provides technical existence proof*

- 15 Jan 2002

## At Reduced RF Duty Cycle of ~1%, the Front End is a Commercial Product

**CUSTOM LINAC SYSTEMS**
- AccSys’ proprietary and patented linac technology can provide a wide range of ion beams and energies for specialized applications in research and industry. AccSys experts will design a system to customer specifications consisting of a carefully selected combination of our standard modular subsystems: radiofrequency quadrupole (RFQ) linacs, drift tube linacs (DTL), rf power systems and/or other components such as high energy beam transport (HEBT) systems and buncher cavities.
***Radio Frequency Quadrupole Linacs***

- AccSys’ patented Univane (US Patent No. 5,315,120) design provides a robust, cost-effective solution for low-velocity ion beams. This unique geometry incorporates four captured rf seals, is easy to machine, assemble and tune, and is inexpensive to fabricate. The extruded structure, which is available in lengths up to three meters, can accelerate ions injected at 20 to 50 keV up to 4 MeV per nucleon. Cooling passages in the structure permit operation at duty factors up to 25%.

- Drift Tube Linacs provide a cost-effective solution for ion beam energies above a few MeV per nucleon. Designed to accelerate ions from an RFQ, the DTL’s permanent magnet focusing and high rf efficiency result in a minimum cost per MV. AccSys’ patented drift tube mounting scheme (US Patent No. 5,179,350), which is integral to the twin-beam welded vacuum tank, provides excellent mechanical stability and low beam loss.

***Drift Tube Linacs***

*D. Young’s work...*

- 15 Jan 2002

## Commercially Available Front-End Linac (AccSys)

- Don Young has verified the applicability of the AccSys RFQ/DTL to various PD scenarios.
- This is a real product.  Accsys has shipped multiple RFQ/DTL units for medical purposes in recent years.
- Estimate ~$20M for turn-key operation @87MeV
-  (Less if FNAL provides the RF/Klystron/modulator)
- This is very interesting for FNAL to pursue no matter what becomes of PD2 study.

- 15 Jan 2002

## AccSys Source/RFQ/DTL

- Appears to have shorter length and lower price than cloning the SNS Linac, _*for 10 Hz operation*_

- AccSys PL-7 RFQ with one DTL tank

*D. Young’s work...*

- 15 Jan 2002

## SC Linac:  87 -186 MeV

- Replace Cavity-Coupled (Warm) Linac of SNS design with 805 MHz Superconducting Linac
- Cold quads and long cryomodules reduce length to ~25m
- Use Beta=0.47 Cavities developed for RIA by INFN/Jlab/MSU  collaboration
- RF fanout with fast phase shifters on each cavity

- 15 Jan 2002

## SC Linac: 186 - 400 MeV

- Same Cavities, Couplers, etc. as SNS “medium-Beta”
- Higher assumed gradients reduce # cavities from 33 to 24
- Cold quads and long cryomodules reduce length to ~35m

- 15 Jan 2002

## SC Linac: 400-1150 MeV

- Same Cavities as SNS “High-Beta”
- Same assumed gradient and # cavities as SNS
- ( higher assumed gradient could raise output energy above 1 GeV )
- Cold quads and long cryomodules reduce length to ~60m

- 15 Jan 2002

## “TESLA” style Linac:  1  8 GeV

- 30 TESLA-style  Cryomodules
- 30 Klystrons with 10:1 TESLA-style RF fanout
*	**	**( requires fast phase shifters/attenuators on each leg )*
- 480 m length for 1.3  8 GeV

- 15 Jan 2002

## Self-Consistent Accelerator Physics Design(Jim MacLachlan)  

-    Had to increase number of quads to get to good design...

- 15 Jan 2002

## Superconducting Cavity Gradients

- 8 GeV design
- assumes *peak*
- field in cavities
- of 45 MV/m.
- SNS:
-     37.5 MV/m
- TESLA(500):
- 	47 MV/m
- TESLA(800):
- 	~70 MV/m

- 15 Jan 2002

## SNS Cavity Fabrication

- Deep drawing & machining

- Dumb-bells

- Frequency adjust

- Welding

- SNS =0.61

- Tuning

- 15 Jan 2002

## SNS  = 0.81  Tests at TJNAF

**Eacc > 20 MV/m for protons **
**is now reasonable design goal**

*[ from N. Holtkamp Nov ‘01 SNS Review]*

- 15 Jan 2002

## SNS Cavity Costs

- SNS recently ordered 109 cavites 1.2m long for:      ($4M Niobium + $4.5M fab & process)                 ~ $80k per cavity
- The 8 GeV Linac needs 380 cavities 1.2m long                      (~ 400 including spares)    $32M for 8 GeV
- This assumes:
- no quantity discount or rebate for existing tooling
- that 1.2 GHz  9-cell cavities are the same price as 805 MHz  6-cell SNS cavities of same length
*  **** **The cavity cost should not blow the budget*

- 15 Jan 2002

## CRYOMODULES

- _BIG Differences between SNS & TESLA_
- Key Specification:
- SNS Cryomodules can be swapped out in _*~1 shift*_
- TESLA cryomodule failure take _*25 days*_ to fix
- comes from having 2.5km section of linac
- 8 GeV LINAC:  _*~2 day*_ repair time specified
- possible because linac sector is much shorter ~300m

- 15 Jan 2002

## SNS/CEBAF Cryomodules

- Warm-to-cold beam pipe transition in each module
- 2K Coldbox, J-T & HTX in each Cryomodule
- Bayonnet disconnects at each coldbox
- Only 2-4 cavities per cryomodule
*Expensive Design forced by fast-swap requirement*

- 15 Jan 2002

## TESLA-Style Cryomodules for 8 GeV( T. Nicol )

- Design conceptually similar to TESLA
- No warm-cold beam pipe transitions
- No need for large cold gas return pipe
- Cryostat diameter can be *smaller* than TESLA (same as LHC)

- 15 Jan 2002

## Scaling of TESLA Cryomodules for 1-8 GeV

- _Frequency_: 1300 MHz  1207.5 MHz
- for compatibility with 805 MHz front-end Linac
- 1.2 GHz cavities must be ~ 8% larger than TESLA
- 8 Cavities per Cryomodule not 12 (TESLA)
- _Accelerating Gradient for Protons _
- Assume Eacc ~ 23 MeV/m (Epeak~45MV/m)
- Protons Linacs must run off-crest for phase stability (cos ~ 0.9)
- _Number of Quadrupoles_
- 8 GeV requires 2 quads per 16m cryomodule not 1/3
- Quads must be long ~1m to avoid H- stripping from B-field
- _Vacuum Breaks_: every ~ 80m not 500m  (design choice)

- 15 Jan 2002

## Scaling of TESLA Cryomodules for 1.3-8 GeV

- 15 Jan 2002

## CRYOGENICS & CRYO PLANT

- 8 GeV Linac Cryoplant is ~ same size as SNS
- Linac is longer: 8 GeV vs. 1 GeV
- RF Duty Cycle is smaller 1% vs. 6%
*Dynamic heat load is about the same*
- 8 GeV Linac Static heat leak per meter should be similar to TESLA (TTF)
- No bayonet or cold box heat loads per cryomodule
*Standby heat load should be < ~  SNS*

- 15 Jan 2002

## CRYOGENICS & CRYO PLANT

- Arkadiy Klebaner is doing detailed analysis of 8 GeV linac cryogenic requirements & cost

- 15 Jan 2002

## SNS CHL Facility

_*8 GeV Linac Cryoplant will be comparable ~$15M*_

- 15 Jan 2002

## RF System for 1 8 GeV Linac

- Assume the TESLA-style RF distribution works
*This will require development of fast phase shifters for individual cavity control*
- One TESLA multi-beam Klystron per Cryomodule
- 24 Klystrons  10 MW each
- Each Klystron feeds 12 Cavites in one Cryomodule
- 288 total power couplers  600kW each
- Modulators are identical to TESLA modulators
- Rough Cost:  $1.5M / RF station    $45M
- (TESLA costs & scaling rule* gives ~ $31M)
- 					*cost proportional to (quantity)-0.074

- 15 Jan 2002

## Modulators for Klystrons

- Biggest component in RF costs
- Pfeffer, Wolff, & Co. have been making TESLA spec modulators for years
- FNAL Bouncer design in service at TTF since 1994
- $1M ea.

- 15 Jan 2002

- 15 Jan 2002

## 8 GeV Linac - Siting for Design Study

- 15 Jan 2002

## SNS Tunnel & Klystron Gallery

- SNS Klystron Gallery costs ~4x Linac Tunnel

- 15 Jan 2002

## SNS Tunnel & Klystron Gallery

*SNS:*
*One Klystron *
*every ~3m *
*along beam *
*line*
*(TESLA: 50m)*
*(8 GeV: 16m)*

- 15 Jan 2002

## Note on Klystron Location

- The SNS Civil Construction (Klystron Gallery) costs could be reduced _a lot_ if we adopt the TESLA scheme of putting the Klystron and instrumentation electronics in the tunnel, and running a fat cable to a single building with all of the modulators in it.
- This may not be an acceptable technical risk.
- In any case we save by fanning out RF drive to many cavities from small # of big Klystrons

- 15 Jan 2002

## TESLA Tunnel & Klystrons

- 15 Jan 2002

## SOME TECHNICAL ISSUES

- Main Injector Beam Current Limits
- RF Power
- Beam Stability
- H- Stripping & Injection at 8 GeV
- stripping in bend magnets
- foil issues
- RF Phasing in Linac for Protons vs. Electrons
- transit time factors in cells and cavities
- phase agility required of RF drive (microphonics)
***  *_*all these must be looked at but none seem fatal*_

- OK up to 1.5E14 (=5x MI design) with RF upgrade      *(W. Chou PAC ‘97)*

- 15 Jan 2002

## Main Injector RF Limitations

- Existing RF System Limits  *(D. Wildman)*
- 4.5 E 13  (~0.7 A)   0.6 MW beam power
- limited by beam stability given present primary amplifier tube power  (installed power = 3.6 MW pk.)
- may be increased with fast, local feedback
- Install Second Power Tube in MI RF Cavities
*	**	**(this is provided for in the cavity design)*
- 9E13  (~ 1.4 A)   1.2 MW beam power w/o feedback
- Possible limits from cavity drift tube cooling
- Two tubes/cavity + fast feedback may reach 2MW
- otherwise may need to build more cavities

- 15 Jan 2002

## 8 GeV H- Stripping in Magnets

- B= 0.06 Tesla strips only 1E-6 of Beam in 10m length
- 500m Bend Radius is OK
- Stripped Beam Power is <1 Watt

- 15 Jan 2002

## 8 GeV Injection Line Opticswith Betatron and Momentum Collimation

- 15 Jan 2002

## H- Injection Layout in MI

- Foil Stripping Injection at 8 GeV
- Slow orbit bump disappears as beam accelerates
- (fast, smaller orbit bump also required to escape foil)
- Injected beam misses nearest quad in MI straight section

- 15 Jan 2002

## Other H- Injection Issues

- multiple scattering in the foil
- foil lifetime
- beam dump for partially-stripped beam
- irradiation of the downstream area
- space charge tune shift limit in Main Injector
- phase space painting
- fast orbit bump & painting magnets
*** **does not look like any of these are problems*

- 15 Jan 2002

## H- Injection Painting(A. Drozhdin)

- Painting from 2pi into 40pi with 90-turn injection seems feasible
- Peak foil temperature ~2200 degC     (tolerable)

- 15 Jan 2002

## RF Phasing in Linac for Protons vs. Electrons

- Cavity cell length changes as proton accelerates
- not all cavities can be same design
- lose some gradient by running off design 
- Protons are non-relativistic
- energy error  downstream phase error
- Protons run off-crest
- only get ~85% of accelerating gradient at crest
- more sensitive to phase errors
- Must change cavity phases to accelerate electrons and protons on alternate cycles

- 15 Jan 2002

## How much gradient do you lose by running cavities at the wrong  ?

- 15 Jan 2002

## CAVITY MICROPHONICS

- Cavity Bandwidths     are  ~ 1 kHz   (Q~106)
- Mechanical vibrations can shift resonant freq. by comparable amount.
- Produces large shift in required *phase* and *amplitude* of RF drive
- Codes exist to simulate impact on proton beams from measured (SNS/TESLA) microphonics.

- 15 Jan 2002

## Fast Ferrite Phase Shifter R&D

- Provide fast, flexible drive to individual cavites of a proton linac,  when one is using TESLA-style RF fanout.
- Also needed if Linac alternates between e and P.
- The fundamental technology is proven in phased-array radar transmitters.
- This R&D was started by SNS but dropped due to lack of time.  They went to one-klystron-per-cavity which cost them a lot of money (~$20M).

- 15 Jan 2002

## “SNS March 2000” Design, 12 Cavities / KlystronIndividual + Collective Cavity Control

- SNS pursued & dropped due to lack of R&D time

- 15 Jan 2002

## SNS Final Baseline RF Design 1 Klystron Per Cavity, Individual Control

- Conceptually simpler but ~10x more Klystrons

- 15 Jan 2002

## RF Fan-out for 8 GeV LinacA. Moretti, D. Wildman

- 15 Jan 2002

## RF Fanout at Each Cavity

- 15 Jan 2002

## 805 MHz RF Distribution in Tunnel

- 15 Jan 2002

## SECONDARY MISSIONS

- _Main Mission:_ “Super-Beams” in Main Injector
- _Possible Secondary Missions:_
- 1)   8 GeV Neutrino Program
- 2)   8 GeV Spallation Neutron Source
- 3)   8 GeV Fixed-target Program
- 4)   -factory front end
- 5)   Electron Linac
- 6)   XFEL
- 7)   Recirculating microtron (pseudo-CEBAF)
- 8)   Pbar Deceleration
- 9)   TESLA damping ring preaccelerator linac .....
-                                     *...etc... etc...* *etc...*

- 15 Jan 2002

## Possible Secondary Mission #1: 8 GeV Neutrino Experiments

- 8 GeV beam for Mini-BooNE follow-on
- Interleave one 8 GeV cycle(s) with MI filling
- > 3.6E17 Protons/hr to *both* MI and BooNE
- Upgrade potential for >10 MW of 8 GeV beam
- ~ 20% efficiency wall power  beam
*Mini-BooNE confirms the LSND result, the 8 GeV linac could help increase statistics >20x.*

- 15 Jan 2002

## Demand Schedule for 8 GeV Protons

- 8 GeV
- Linac
- >1E18/hr

*R. Webber*

- 15 Jan 2002

## Possible Secondary Mission #2: 8 GeV Spallation Neutron Source

- Upgrade RF Duty cycle from 1% to ~5%
- RF, couplers, and cryo pipe sizes must anticipate this
- Add SNS-Style Accumulator Ring    (R ~ 50m)
- Biggest incremental cost will be Target facility

***8 GeV Linac has the potential be competitive as a pulsed neutron source,  if FNAL is interested...***

- (Installed Klystron peak power ~300MW vs. ~50 MW in SNS)

- 15 Jan 2002

## Possible Secondary Mission  #3: 8 GeV Fixed-Target Program

- Pion production per incident beam energy is maximized at ~6 GeV        *(N. Mokhov)*
-  Best source for precision , K experiments.
- The RF time structure (~50 psec bunches) would allow high-quality TOF separation of neutral K’s
- The Recycler might be used as 8 GeV stretcher ring to provide ~ continuous beams of protons.

- 15 Jan 2002

## Possible Secondary Mission  #4: Neutrino Factory

- Very Similar to 8 GeV Spallation Source
- (but shorter time spread on target)
- Possible to use _*same linac*_ to _*re-accelerate *_the muons after filling the accumulator ring?
- 1) use linac to fill the 8 GeV accumulator for ~1 msec.
- 2) rephase the cavities for muon acceleration (~0.2 ms).
- 3) bunch the accumulator beam and extract onto target.
- 4) debunch & cool the muons in couple sec
- 5) reaccelerate the muons in *same* linac at 8 GeV/turn.
- 		 *everything uses DC magnets.*

- 15 Jan 2002

## The competition:1.3 GeV SC Linac  for AGS Upgrade

- 1.3 GeV
- Superconducting Linac Upgrade

- T. Roser  PAC 2001

- AGS Beam Power ~ 2MW

- 15 Jan 2002

## Possible Secondary Mission #5: 8 GeV Electron Linac

- At least 7 GeV of the linac can accelerate e-
- electrons run on-crest, so the gradient will be higher     9-10 GeV e-beams
- Re-phase the cavites for (multiple) pulses of electrons between proton injections to FMI.
- Many possible physics missions, test beams, etc.
- Smaller activation problems than proton beams
- An 8-GeV Linac and SCRF infrastructure makes FNAL a good site for a super-B-factory...

- 15 Jan 2002

## Possible Secondary Mission #6: X-ray Free Electron Laser (XFEL)

- There may be competition for XFEL’s in the U.S.
- FNAL may want to stay out (or collaborate).
- Concept of joint ANL-FNAL-DESY project, (sister XFEL’s at DESY and FNAL),  with ANL taking the lead on US XFEL user facility...?

- 15 Jan 2002

## Possible Secondary Mission #7: Recirculating Electron Linac

- A CEBAF-Style Recirculating Linac could be made with   ~  8 GeV per pass
- Smaller Duty Cycle than CEBAF,  but higher energy per pass.
- Either MI or MR tunnels could hold stretcher ring to provide ~ continuous beams of *electrons.*

- 15 Jan 2002

## Possible Secondary Mission #8: Antiproton Deceleration

- Scenario:
- 1) Electron-cool Antiproton Beams in Recycler
- 2) Ultra-cool core can be frictionally dragged away and separately extracted
- 3) Small emittances will decelerate efficiently   in large-aperture SC Linac
-  World’s best source of “stopped” antiprotons

- 15 Jan 2002

## VLHC and the 8 GeV Injector

- The small beam emittances obtainable with the 8 GeV Injector will make FNAL *by far* the best VLHC injector.
- Small Emittances  Small Beam Currents at fixed Luminosity
-  Small Stored Energy in Beams
-  Small instability problems in small beam pipes ( Small magnets)

- 15 Jan 2002

## Proton Driver vs. 8 GeV Injector

- There is little doubt that, in principle, a synchrotron is cheaper.
- If we are manpower limited:  an 8 GeV Linac has many fewer parts to design than a new Booster Synchrotron.
- The 8 GeV linac will probably be simpler to operate.
- The 8 GeV linac is more likely to produce smaller emittances, if that is the primary goal.
- It can accelerate electrons, and so has a broader range of uses.
*Difficulty with reconciling Proton Driver with B&B subpanel recommendations can be finessed by 8 GeV Linac.*

- 15 Jan 2002

## The Linear Collider & 8 GeV Injector

- If the plan is the LC, will be an advantage in asking for this $7B project to have already completed a _*~1% proof-of-principle facility*_ showing that we understand the performance and costs.
- However in the current political climate, it may be _*difficult to ask for a $100M+ proof-of-principle*_ facility as the _*leading edge of a $7B project*_  (GWF opinion).
- FNAL needs a construction project ~ 2004 when NUMI & LHC money starts vanishing.  _*Need to get a project into the pipeline NOW*__.__ _
- The 8 GeV linac has _*good, stand-alone physics missions*_ and will simultaneously _*provide $200M+ “LC R&D” funds*_ to demonstrate that we understand the performance and economics of big linacs.
- Since _*only the TESLA design can accelerate protons*_, it simplifies the LC technology choice, which can be made promptly and without contentious technology and cost comparisons.

- 15 Jan 2002

## Many Other Users of SCRF Linacs

- 15 Jan 2002

## The Linear Collider & 8 GeV Injector (cont’d)

**If TESLA is approved in the next couple of years,** then the 8 GeV Injector gives the US the opportunity to extract some benefit from our contribution to SCRF Linac technology. *(makes it easier to argue for a US contribution to TESLA if there is a simultaneous construction project with related technology in US)*
**If TESLA  is  NOT immediately approved,** and only TTF-2 and the 8 GeV Injector are completed,then by ~2009 this will leave the US holding the *strongest technological position to bid for the LC.**(and 8 GeV linac can be used for TESLA Damping ring pre-acc.)*
- The 8 GeV Linac holds the best promise of retaining the current construction slots in HEP (namely NUMI and the LHC),while remaining true to the strategic vision of the B&B subpanel.

- 15 Jan 2002

## CONCLUSIONS

- An 8 GeV Injector Linac will be a useful component at FNAL no matter what future machine is built.
- There are no technical difficulties, just further optimizations.  Can copy existing designs.
- It should make FNAL complex simpler to run.
- The cost could be similar to the Main Injector and Proton Driver.

- 15 Jan 2002