FNAL Feasibility Study on a Neutrino Source Based on a Muon

Storage Ring

• Results from recent technical discussions

• some nice technical solutions

• some results with impact on the physics study

• Status of the study

• Timing

Norbert HoltkampFardog Summary, Jan. 6th ‘00

The Task

• A design concept for a muon storage ring and associated support facilities that could, with reasonable assurance, meet performance goals required to support a compelling neutrino based research program.

• 2.Identification of the likely cost drivers within such a facility.

• 3.Identification of an R&D program that would be required to address key areas of technological uncertainty and cost/performance optimization within this design, and that would, upon successful completion, allow one to move with confidence into the conceptual design stage of such a facility.

• 4.Identification of any specific environmental, safety, and health issues that will require our attention.

Choice has been made !

• Basic Calculation– 1/3 of the muons decay in the straight section (38 %)– 10 protons for 1 into the storage ring (>10; >20-50)– 2x107 sec

• 2x1013 proton on target per pulse @ 16 GeV and 15 Hz– 3x1013 proton because of carbon target

• 2x1012 per pulse to be accelerated and injected into the ring– cooling channel not successfully simulated < 2x1012

• longer bunch in the proton driver and on target (1 nsec 3)– helps

• ring tilt angle is 13deg ( 22 %) instead of 35 deg (57 %)– ring with these params. Is not a cost driver at all

Parameters for the Neutrino Source

- Energy of the ring GeV 50

- Number of neutrinos / straight

2x1020/y

- no polarization

- capability to switch between

- FERMI to SLAC / LBNL

The Neutrino Source

• Approach:– go more conventional where ever possible

– Oak Ridge, FHML, Brookhaven the target• most people bought the solid target

– Jefferson Lab / Cornell sc rf and re-circulating linacs• biggest disconnect right now

– LBNL , DUBNA induction linacs (talk tomorrow)• goes much better than expected but not cheap

– IHEP Protvino sc solenoid channels• so far very good job

– specific design and engineering (cooling channel, target collection, beam manipulation, beam tracking and simulation) Muon Collider group (12 people @FNAL) + the collaboration

• ( thank Andy for the enormous support)

– general engineering (large scale rf systems, sc magnets, sc solenoid channels, ps, vacuum, beam lines, tunnel, water) (20 FTE for 6 month)

• very good support from FESS and TD

• not easy to convince somebody in BD that anything else than TEVATRON is useful at all.

The Neutrino Source

• First experiment based on an intense muon source -> does it have to be 50 GeV ??– 10 GeV and 50 kT or more magnetized water detector: Goal: Balance

detector cost with Accelerator: E*kT*I=const.

– Start with 2x1019/year (Sessler, Geer) and still good physics

Parameters for the Muon Storage RingEnergy GeV 50decay ratio % >40inv. Emittance m*rad 0.0032 in straight m 160N/pulse 1012 6typical decay angle of mrad 2.0Beam angle (( mrad 0.2Lifetime c* m 3x105

Neutrino Source Study @ FERMI

• Application of a “Generic Neutrino Source” to specific site

• Base the study on specific set of Parameters

• 6 month period of time to define the R&D program and develop a layout to investigate the scope of such a complex

Physics Study in parallelH. Schellmann / S. Geer

Generic Layout

collaboration paper

“deviate wherevernecessary or useful”

Footprint for a 50 GeV Neutrino Source

• Infrastructure is very close together ...

R & D Issues for the Proton Driver Design Study

• R & D groups:• Goal:

–4 x 0.75x 10-13 = 3x 10-13 @ 15 Hz

–8 GeV versus 16 GeV versus higher energies ?•Very hard to get people going on this: Only Chuck A.

•Will probably not appear in the report in detail

• Why?–Power bill is dominated acceleration

–at low Frequ. Tfill is large compared to T pulse

–most of the time power source is on for filling

– -> higher rep rate less efficient; peak current is limit too.

–Go to higher energies (more acceleration): Higher Proton beam energy and smaller rep rate is more efficient way to produce beam power

What changes compared to MC

• The target– Ptarget is still of the order of 1.5 (graphite) with upgrade possibility to 4 MW (probab. Liquid)

– RF after target only gives increase in Polarization from 28% to 40% -> it is not worth it !! A. Blondel from CERN

– Target dissipation is only 30 kW or so -> radiation cooled– Radiation damage is a major constraint for sc coil. 0.5 - 1 year is most probable lifetime so far– 20 T can only be achieved with sc +nc coil.– Disagreement between people on the fatigue limits calculated and the actually NuMI test.

30 - 60 MHz rf~ 5 MV/m

Target for a Neutrino Factory

• 1 - 2 MW target• Reduce power in the target -> low Z• Solid Target: loose x 1.5 in yield -> more protons -> ok at this

intensity• Magnet radius is too small, especially with Copper inside

Induction Linacs and Long Solenoidal Channels

50 m drift before 50 m drift before rotation rotation

For carbon target:0.10 /p between 225 - 240 MeV0.13 /p between 220 - 250 MeV0.18 /p between 200 - 270 MeV

Trade off:•Energy Spread after rotation drift channel length [loss]•Particle capturelength(voltage) in induction linac [loss]

simplest solution offers comparable yield

Induction Linac Layout

• Strong Effort at LBL for DAHRT• A little bit of expertise at Fermi

– higher field 2-3 T and smaller cores may be better solution

– saturation in the cores is under control

– switching is the main problem

Small effort at FNAL: “old” expert from DUBNA no working in TD.

Mainly on solenoid channel design

LBNL Status

• Induction Cell– basically ok. Trade off between: operational and investment cost

• Pulser system:– still not so clear: 4 pulse per burst…

– asymmetric voltage

–

The Heart of the Cooling Channel

for a Neutrino Factory

• IIT, BNL, LBNL, FNAL: go through an engineering design faster

• Goal: Do all the cooling with one set of hardware RF may be, solenoids no

• Analytical (Courant Snyder type description of the motion in Solenoidal channel) LBL

Bz ~ 5 T maxEacc ~ 15 MV/m @ 200 MHz

The Cooling Channel

• +/- 3.5 T up to 5T or more Lattice with 15 MV/m 175 MHz rf• period gets shorter and shorter

Reduces to about 100-140 m of cooling channel

200 MHz Cavity + Power Source

• Engineering Layout required for the study• Want to build and test it, once study is done

1/8th of the full accelerating cell

~ 0.65 m

~ 0.65 m

Enhance the E Fieldon Axis by using a grid

Goal: 15 MV/mnc cavities

Acceleration based on RLA

• Why not nc?– Peak power limited already

– in normal conducting cavity: too much power required to build up the gradient

– gradient is not a free parameter for optimization:• muon decay +longitudinal acceptance

• SC structures at 200 MHz (100 MHz) and 10 MV/m (7,5 MV/m real estate)– almost no power to build up gradient --> beam

– loaded Q’s are similar to nc structures ->fill time short but coupler ? -> comparatively efficient !

– 4 x 30 bunches per RLA, 2.5x1012 total

– Plinac ~ 6 MW, PRLA1 ~ 2 MW, PRLA2 ~ 12 MW

– ~20 MW power for RF acceleration at ~25 % overall efficiency (AC RF)

– Problem is the required peak power not average power !

RLAEnergy

Ltot

mLlinac

mIbeam

mARloaded

M/mQloaded Nr of

turnsTpulse =

Tfill+Tacc /sPeak

PowerMW/m

2-10 800 2x135 120 83 80 x103 4 132+10 1.210-50 2400 2x700 40 252 240 x103 4 400+32 0.4

Optimization of the Storage Ring

• The cheapest way to produce muons in the straight section is to make them as long as possible !

= Nr of decaying in straight section

Nr of injected

= 1

2 (1+ /L)

B / Tesla

1

2 (1+0.2) =L=length of straight

• Problem with dynamic aperture due to short Magnets and large aperture (10x15 cm) -> not fixed yet

The SC Large Bore Magnets

• Low field quality helps reduce price although large aperture• main heat load due to -decay, probably not optimum• 1 cm tungsten liner instead of 3 cm

Large Bore Magnets

• Similar magnets for the RLA Arcs with less tungsten shielding

• Bigger magnets in the Beam Spreaders of the RLA arcs + combined function

• Energy Acceptance of the Arcs ??????

Storage Ring Arc Cell

The Storage Ring Location@ FNAL

Storage Ring Layout

• Site layout for the Storage Ring and the Arcs• Experimental beam lines and halls• Cryo space requirement

Goal & Schedule

• 6 Month study: “10 pages of paper per subsystem+ 1 schedule + 1 cost”– Internal Review Feb. 15th and 16th for the Accelerator part, Feb.

17th and 18th for Geer/Shellman to align the different contributions

– Documents in by beg. of march– Report out by March 30th if that’s acceptable

• Most risky– induction linac (no, only expensive ->R&D)– cooling channel design and performance

• what is the minimum emittance achievable• it is still the most unreliable item

– acceleration: ( largest cost driver)• Jefferson Lab Cornell CERN SLAC Fermi• after Feb. 15th & 16th have working meeting with these groups to go

through: Cryo, cavities, couplers and power sources• not sop clear how to organize it

Cost

• Hot Topic: Preliminary result.Cost Total for each Sub-System

0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0%

Proton Driver

Target Systems

Decay Channel

Induction Linac

Mini Cooling

Adiabatic Capture

Cooling Channel

Capture Linac

RLA 1

RLA2

Storage Ring

Su

b-s

ys

tem

s

percent of total

0.0% 10.0% 20.0% 30.0%

Magnets

RF Source

RF Cav

Vacuum

PS

Diagn.

Cryo

Utilities

ES&H

Civil

Sy

ste

ms

percent of total

Questions

• What comes after the study ?– Review the results

– Does the lab want to do this ?– If done or obvious: Define the R & D program

• remember: 10 different subsystem and all need strong R&D program … a lot of people, time and money.

– Develop efficient and cost effective accelerating systems at low frequency

– Prepare a site where this experimental program can be pursued

– leading role for Muon Cooling

Directors office