# Presentation: 478221

## MCTF ACTIVITES

- Andreas Jansson

## “

- If you can’t decide which new projects or ideas to bet on based on their
- objective merits, pick those that will be developed by the most committed
- and persuasive heretics

*from “The weird rules of creativity” by Robert I. Sutton*
*Harvard Business Review, 2001*

## Charge

- Andreas Jansson         AAC Review May 6-8, 2008

- The Committee is asked to review the activities of the MCTF and NFMCC activities at Fermilab, and offer comments on the strategic approach, the appropriateness of program goals (including with respect to timing), and the technical progress towards achieving these goals. The committee should note that the national Muon program will have been reviewed by the Muon Technical Advisory Committee four weeks before the AAC meeting. As such the AAC is specifically asked to **concentrate on Fermilab’s contributions to these programs**. In formulating its comments and recommendations the committee should consider, and offer advice as appropriate, on the interaction between these activities and the broader national and international muon programs.

## Overview of MCTF activites

- Collider scenario
- Collider ring design
- RF & power consumption
- Cooling channels
- RFOFO snake
- Helical Cooling Channel
- High Pressure RF test / MTA beamline
- HTS / High field solenoids

- Andreas Jansson         AAC Review May 6-8, 2008

## Collider Scenarios

- Andreas Jansson         AAC Review May 6-8, 2008

- 			Low Emit.	High Emit.	MCTF07
- s  (TeV)				1.5
- Av. Luminosity (1034/cm2/s) *	2.7	1	1.33-2
- Av. Bending field (T)		10	6	6
- Mean radius (m)		361.4	500	500
- No. of IPs			4	2	2
- Proton Driver Rep Rate (Hz)	65	13	40-60
- Beam-beam parameter/IP	0.052	0.087	0.1
- * (cm)			0.5	1	1
- Bunch length (cm)		0.5	1	1
- No. bunches / beam		10	1	1
- No. muons/bunch (1011)	1	20	11.3
- Norm. Trans. Emit. (m)	2.1	25	12.3
- Energy spread (%)		1	0.1	0.2
- Norm. long. Emit. (m)		0.35	0.07	0.14
- Total RF voltage (GV) at 800MHz	407103c	0.21** 	0.84**
- Muon survival N/N0		0.31 	0.07	0.2
- + in collision / proton		0.047 	0.01	0.03
- 8 GeV proton beam power	3.62*** 	3.2	1.9-2.8
- ---------------------------------------------------------------------------

- *) Luminosity calculated taking account of the hour-glass factor but ignoring the dynamic beta effect.
- **) Momentum compaction in the present ring design c=1.510-4. Note that it would be better to assume f=1.3GHz to keep the RF voltage at a reasonable level (0.52GV for MCTF07 set)
- ***) Assumes  /p ratio of 0.15 after capture and precooling, and only decay losses afterwards. Positive and negative muons are assumed to be produced independently (from different protons).

- Y. Alexahin

## Proton driver

- An upgraded Project X linac looks very attractive as MC proton driver
- 8GeV high rep rate or
- Acceleration to ~50GeV in MI
- Started looking into the specific upgrades that would be required
- Feedback to Project X design team

- Andreas Jansson         AAC Review May 6-8, 2008

- C.Ankenbrandt *et al*

## Collider ring design issues

- Andreas Jansson         AAC Review May 6-8, 2008

- Y. Alexahin
- E. Gianfelice-Wendt

- (Small circumference, low beta*)

## “Dipole First” optics

- Andreas Jansson         AAC Review May 6-8, 2008

- Y. Alexahin
- E. Gianfelice-Wendt

## Recent design studies results

- Andreas Jansson         AAC Review May 6-8, 2008

- Work ongoing....

- Y. Alexahin
- E. Gianfelice-Wendt

## RF issues

- Andreas Jansson         AAC Review May 6-8, 2008

- Feature of the muon collider linac :
- high bunch population, 1÷21012
- ILC linac – 21010.
- Problems:
-     Strong cavity loading by a single bunch;
-     Energy spread in the bunch;
-     Bunch timing;
-     Transverse kick and emittance dilution.
-     RF – kick
-     Muon decay electrons (heat load)

- For N=2e12, f=1.3 GHz
- (ILC-like structure)
- and σ=8 mm Wmax= 6.2 MV/m!

- N.Solyak
- V.Yakovlev

## Bunch timing issues 

- Andreas Jansson         AAC Review May 6-8, 2008

- Acceleration gradient along linac,
*Red -one direction, *
*Blue-opposite direction*

- N.Solyak
- V.Yakovlev

- Preferred
- by RF

- Preferred
- machine
- design

## Total power estimates

## First look at RLA power requirements

- Andreas Jansson         AAC Review May 6-8, 2008

- HE2008, 1.5 TeV

| 
N | Muon  losses,
% | RF power, MW | Total cryogenic losses, MW | Losses in HOM couplers, MW | Total powerMW | Number of
klystrons (10 MW) | Number of cavities | Average klystron power, kW |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 10 | 6.4 | 20 | 4.8 | 1.5 | 24.8 | 180 | 2920 | 59 |
| 20 | 9.3 | 16 | 3.8 | 2 | 19.8 | 122 | 1460 | 70 |
| 30 | 11.1 | 14 | 3.5 | 2.2 | 17.5 | 92 | 973 | 81 |

- LE2008, 1.5 TeV

| N | Muon  losses,% | RF power, MW | Total cryogenic losses, MW | Losses in HOM couplers, MW | Total power, MW | Number of
klystrons (10 MW) | Number of cavities | Average klystron power
kW |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 10 | 6.4 | 68 | 13.9 | 1.8 | 81.9 | 90 | 2920 | 402* |
| 20 | 9.3 | 48.6 | 8.7 | 2.5 | 57.3 | 61 | 1460 | 424* |
| 30 | 11.1 | 42 | 7.4 | 2.8 | 49.4 | 46 | 973 | 486* |

- Available 10 MW klystrons have an average power of 150 kW.

- N.Solyak
- V.Yakovlev

## New cooling channel idea: FOFO snake

- Andreas Jansson         AAC Review May 6-8, 2008

- Y. Alexahin

##  HCC “rules of thumb”

- Independent investigation of HCC by Balbekov shows that:
- Equilibrium emittance is proportional to helix period (and is higher for HCC compared to e.g. Guggenheim lattice).
- 1-2mmrad at 1m helix and 250MeV/c
- There is an optimal ratio between RF frequency and  helix period. The cavity size roughly scales with the helix period.
- 200MHz @ 1m, 400MHz @ 50cm, etc
- Obtainable cooling factor (ratio of acceptance and equilibrium emittance) is ~4.5 in each plane, 6D cooling ~90x.
- Further cooling requires shorter helix (higher B field and RF frequency).

- Andreas Jansson         AAC Review May 6-8, 2008

- V. Balbekov

## Frequency and energy dependance

- V. Balbekov

## HCC magnet design

- HCC requires superimposed solenoid, helical dipole and helical quadrupole fields
- Helical solenoid (HS) use smaller coils than a “traditional” design
- Lower peak field
- Less stored energy
- Lower cost
- Field components in HS determined by geometry
- Over constrained
- Coil radius is not free parameter

- Andreas Jansson         AAC Review May 6-8, 2008

- Vl.Kashikin

## 4-coil Helical Demonstration Model

- Goals:
- validate mechanical structure and fabrication methods
- study quench performance and margins, field quality, quench protection
- Features:
- use existing SSC cable
- fields and forces as in the HS for CDE
- Funded by MCTF and Muons Inc.

- Vl.Kashikin
- S.Makarov

## 4-coil fabrication status

- Parts:
- design complete
- procurement in progress
- Cable:
- Extracted strand samples were tested
- Practice winding complete:
- cable stability and support during hard bend winding
- coil size control
- Instrumentation:
- development started
- Model test:
- September 2008

- Vl.Kashikin
- S.Makarov

## HCC demo experiment plans

- Before building a large (and expensive) HCC magnet, would like to know
- How we can include RF in a HCC without loosing cooling performance
- If HPRF works with beam
- The next step would likely be to build a section of such a channel, as an engineering demo.
- A HCC 6D cooling experiment, with or without RF, would happen later.

- Andreas Jansson         AAC Review May 6-8, 2008

## How to implement a real HCC?

- Andreas Jansson         AAC Review May 6-8, 2008

- “Type I”

- “Type 2”

- “Type 3”

- RF inside coil
- Highest possible RF
- packing factor
- Cavity must be smaller than the coil -> high frequency

- RF between coils
- Lower RF packing factor
- Difficult  H2 cryostat design and assembly

- RF and coils separated
- Lower RF packing factor
- Requires some kind of matching between sections
- Likely easier to build and maintain.

## Type 3: Separate RF and helical solenoid

- To be efficient, would need a short(er) matching section.
- Problem: time-of-flight spread in helical section too large to recapture.
- Solution may exist, but not found yet.

- Andreas Jansson         AAC Review May 6-8, 2008

- K.Yonehara

## Required clearance

- Coil and cavity at different temperatures require insulating vacuum gap.
- Estimated required clearance ~3”
- This does not include any RF feed
- Compare to HP H2 cavity radius at various frequencies
- Only low frequency version appear to be plausible.

- Andreas Jansson         AAC Review May 6-8, 2008

| Frequency | Cavity Radius | ratio |
| --- | --- | --- |
| 200 MHz | 55cm (22”) | 88% |
| 400 MHz | 28cm (11”) | 78% |
| 800 MHz | 14cm (5.6”) | 65% |
| 1600 MHz | 7cm (2.8”) | 48% |

- (assuming 200atm H2 )

- 0.4” – 1”

- coil support

- HP cavity

- coil

- insulating vacuum

- ~1.25”

- ~0.8”

- pressurized H2

- ~3”

## Ansys stress simulation

- Andreas Jansson         AAC Review May 6-8, 2008

- Helical pressure vessel

- A.Lee

## Helical Solenoid with correction coils

- At least for later stages of HCC, we will need correction coils
- Relax geometric constraints e.g. by
- Overall solenoid for tuning of Bz component
- Additional helical correction coil(s)for tuning dipole and quad component.
- Dielectrics inside the cavity could reduce cavity size

- Andreas Jansson         AAC Review May 6-8, 2008

**RF cavity**

**Primary helix coil**

**Correction coil**

**Correction coil**

- K.Yonehara

## Series of HCCs

- LEMC'08 Fermilab, K. Yonehara

- 1st HCC:=2.0 m, =1.0
- Primary HS:
- Inner R = 650 mm, Outer R = 680 mm
- Current density = -69 A/mm2
- Correction HS:
- Inner R = 250 mm, Outer R = 280 mm
- Current density = 414 A/mm2
- Solenoid:
- Inner R = 1000 mm, Outer R = 1050 mm
- Current density = -11 A/mm2

**Cooling factor > 10,000**

- 2nd HCC:=1.0 m, =1.0
- Primary HS:
- Inner R = 367 mm, Outer R = 397 mm
- Current density = -129 A/mm2
- Correction HS:
- Inner R = 150 mm, Outer R = 180 mm
- Current density = 387 A/mm2
- Solenoid:
- Inner R = 600 mm, Outer R = 650 mm
- Current density = -31 A/mm2

**200 MHz RF**

**400 MHz**
**RF**

- bsol = -2.7 T, b = 0.86 T, b’/b = -0.84

- bsol = -5.3 T, b = 1.63 T, b’/b = -0.86

## HCC plans

- Now have estimate of required HCC bore to fit HPRF and insulation inside.
- Next step will be to ask TD magnet experts to design large bore magnet with optimal correction coil scheme, in particular for the last HCC section.
- In parallel, develop a real RF cavity design to fit in this space.
- If a promising solution is found, would like to build a section with RF and test.

- Andreas Jansson         AAC Review May 6-8, 2008

## MTA beamline

- HPRF test with beam is critical!
- MTA beam line major activity and budget item this year.
- Switching C-magnets ready to be installed in few weeks
- Linac access required
- RF waveguide reconfiguration required for beam into hall

- Andreas Jansson         AAC Review May 6-8, 2008

- C.Johnstone
- B.Ashmanskas

## First HPRF experiment

- Beam tests will be done in collaboration with Muons Inc
- First test will use the existing Muons Inc test cell
- Will indicate direction of follow-ups experiments
- Linac 400MeV proton beam can generate ionization levels similar to muon beam.
- 6e12 protons ~1.2e13 muons
- Recently approved SBIR Phase I with Muons Inc.

- Andreas Jansson         AAC Review May 6-8, 2008

- beam

- Muons Inc test cell

- Beam simulation

## What we expect to happen?

- Andreas Jansson         AAC Review May 6-8, 2008

- A.Tollestrup

- After a 1⁄4 cycle the electrons have all drifted upward by a distance deltaZ.  This discharges the top plate and leaves a layer of positive charge against the bottom.  The field in this region remains the same and the field outside decreases.  A 1⁄4 cycle later the image is reversed.

- Assume beam passes thru cavity at max Vrf as a delta function

## HCC example

| Emittance | 4.3 mm rad | 1.5  mm rad | .91  mm rad |
| --- | --- | --- | --- |
| Freq | 400 Mhz | 800 Mhz | 1600 Mhz |
| Gradient | 16 MV/m | 16 MV/m | 16 MV/m |

| Beam rms r | 27.6 mm | 12.8 mm | 7.6 mm |
| --- | --- | --- | --- |
| Cavity length | 5.0 cm | 2.5 cm | 1.25 cm |
| Q from plasma | 360 | 157 | 111 |
| Joules Cav | 3.95 | .49 | .0616 |

| Delta Vrf / Vrf | 1 E-4    1.6 E-3 | 2 E-4      3 E-3 | 9 E-4    1.4 E-3 |
| --- | --- | --- | --- |
| Cavity Q no mu | 12886 | 9112 | 6443 |
| Q[1],   Q[16] | 5805   628 | 3343     318 | 1873    161 |

| P cavity  kw | 261 | 249 | 309 |
| --- | --- | --- | --- |
| P gas 1 & 16  | 939 kw   15 mw    | 469 kw   7.5 mw | 235 kw 3.76 mw |

- Andreas Jansson         AAC Review May 6-8, 2008

- A.Tollestrup

## How to remove the ions?

-  **Surface charge = ****************   ;  For instance 100 KV/meter requires a surface charge of ****88 pC /m****2**
**A factor of 10****6 **** less****  ****than the total charge in the ions.**

- The electric field lines simply terminate on the plasma.  I think the main way the ions disappear is thru diffusion to the walls.  This is a slow process.

- Andreas Jansson         AAC Review May 6-8, 2008

- A.Tollestrup

##    Some questions that need answers:

1.  Does something unexpected cause breakdown?  The gas is from the Pashen limit but there could be local action at the cavity surfaces that initiate breakdown.  In general we need experiments to validate our theoretical models.
2.  The free electrons load the cavity.  10e11 looks like near the limit.  Can the electrons be captured fast enough to form negative ions and eliminate this loss by something like SF6? (Note:  SF6 not suitable!)
3.  How does one get rid of the negative ions if one does the above.

- 1.  Does something unexpected cause breakdown?  The gas is from the Pashen limit but there could be local action at the cavity surfaces that initiate breakdown.  In general we need experiments to validate our theoretical models.
- 2.  The free electrons load the cavity.  10e11 looks like near the limit.  Can the electrons be captured fast enough to form negative ions and eliminate this loss by something like SF6? (Note:  SF6 not suitable!)
- 3.  How does one get rid of the negative ions if one does the above.

- Andreas Jansson         AAC Review May 6-8, 2008

- A.Tollestrup

## Follow-up cavity

- Test cell is not an accelerating cavity.
- Several effects we will not be able to study
- Scaling with pressure
- Are the ions a problem?
- Build dedicated cavity!
- Will require MCTF resources in FY09.
- Scale ~1 FTE + ~$200k
- Muons Inc Phase II SBIR?

- Andreas Jansson         AAC Review May 6-8, 2008

- Tunable HP cavity

- M.Popovic

## 50 T Solenoid Conceptual Design Study

**BSCCO**

**Nb3Sn**

**NbTi **

**B**

**Coil radius, m**

- Key design issues:
- superconductor Jc
- effect of field direction on Ic in case of HTS tapes
- stress management
- quench protection
- cost
- Solutions:
- hybrid coil design
- coil sections

- Va.Kashikin

## Towards a National HTS collaboration

- Andreas Jansson         AAC Review May 6-8, 2008

**Development of NbTi and Nb****3****Sn based magnets were developed thru a very successful collaboration between the University Community, the National Labs and the Conductor Manufacturers.  **
**The High Temperature Superconductors operated at LHe temperature offer new and exciting opportunities for magnet design.**
**Alvin has pushed for a National HTS Collaboration to develop and exploit these possibilities:**
**High field solenoids, dipoles, and quadrupoles for HEP**
**NRC panel COHMAG (Committee on High Magnetic Field Research and Technology****) ****set 30 T goal for new NMR and magnets used in scientific studies.**

- A.Tollestrup

## HTS collaboration structure

- Andreas Jansson         AAC Review May 6-8, 2008

_**Technical Committee:**_
- David L.arbalestier   Ch.               NHFMLDan Dietderich                             LBLKen Marken                                  LANL    Lance Cooley                               FNALArup Gosh                                    BNLAl McInturf                                   TA&MEmanuela Barzi                            FNALJustin Schwartz                            NHFML
-  Arno Godeke		LBNL

- Collaboration is taking form
- Modelled after LARP and NFMCC.
- Proposal to be submitted to DOE for $2M annual funding.

- A.Tollestrup

## 1.  Leakage.
2.  Connectivity.
3.  Dependence of Jc on angle wrt B.
4.  Conductor insulation.	
5.  Containing the forces and controlling    	strain.
6.  Quench protection.
7.  Wind and React technology.
8.  Cabling.
9.  Radiation resistance.

- 1.  Leakage.
- 2.  Connectivity.
- 3.  Dependence of Jc on angle wrt B.
- 4.  Conductor insulation.
- 5.  Containing the forces and controlling    	strain.
- 6.  Quench protection.
- 7.  Wind and React technology.
- 8.  Cabling.
- 9.  Radiation resistance.

- HTS Collaboration target areas

- A.Tollestrup

## Ic Angular Dependence at 4.2 K

**Ic Angular Dependence at 4.2 K**

- Bi-2223

- 2G 348

- Detailed measurement of Ic angular dependence for HTS tapes at fields up to 15-16 T
- Most of the Ic reduction occurs between 90 and 45 degrees
- Important information for High Field HTS solenoid design study

- E.Barzi

## BSCCO Rutherford Cables

- Goals:
- increase conductor Ic
- reduce magnet inductance
- Important for magnet quench protection
- Issues:
- Ic degradation after cabling
- Determine design criteria and cabling procedures
- low degradation at packing factors <87%
- Cable HT optimization
- reduce Ag leaks and Ic degradation
- Transverse pressure sensitivity studies
- determine pressure limits

- E.Barzi

##  MCTF Summary

- Significant progress in many areas, despite difficult funding year
- Our most pressing short term goal is to test HP cavity with beam.
- We are also working towards integrating RF into a helical solenoid.
- HTS will be pursued by National Collaboration
- With NFMCC, developing a 5-year plan towards a feasibility study in 2012.

- Andreas Jansson         AAC Review May 6-8, 2008

## Useful references:

- MCTF web site:
- http://mctf.fnal.gov
- BNL MC Design Workshop:
- http://www.cap.bnl.gov/mumu/conf/collider-071203/
- NFMCC Collaboration meeting:
- http://www.cap.bnl.gov/mumu/conf/MC-080317/
- MUTAC Review:
- http://www.cap.bnl.gov/mumu/conf/MUTAC-080408/
- Low Emittance MC Workshop:
- http://www.muonsinc.com/lemc2008/

- Andreas Jansson         AAC Review May 6-8, 2008

## BACKUP SLIDES

- Just some

- Andreas Jansson         AAC Review May 6-8, 2008

##  Balbekovs preferred HCC channel

- The most prospective investigated variants are summarized in table:
**#                                 1             2              3**
**Period length (m)                1            0.5           0.25 **
**Beam momentum (MeV/c)      250          183           183    **
**Frequency**  **(MHz)               200          400           800 **
**Solenoid field (T)               6.96         10.2          20.4**
**Trans.emit1.init/fin (mm)    9.5/2.0      4.6/1.1      2.6/0.55  **
**Trans.emit2.init/fin (mm)****     9.0/1.9      4.6/0.95     2.3/0.48**
**Long. emit.init/fin (mm)      13./3.2      7.1/1.6      3.4/0.81**
**6D emit.init/fin (mm****3****)   1100/12       150/1.6       20/0.22**
**Transmission (%)              87**                   **75            73**

-  Balbekovs preferred HCC channel

- V. Balbekov

## 80cm bore HCC

- Andreas Jansson         AAC Review May 6-8, 2008

- Helical Solenoid Parameters:
- Helix orbit radius 0.255 m
- Coil inner diameter 800 mm
- Superconductor NbTi
- Current 9.7 kA
- Helix period 1.6 m
- Helix pitch 1.0
- Solenoid length 3.2 m
- Coil max flux density  7.0 T

| Field components, R=0.255m, z=1.6 m | HS | K.Y. |
| --- | --- | --- |
| Bz, T | -4.76 | - |
| Dipole Bd, T | 1.074 | 1.05 |
| Gradient dBt/dr, T/m | -0.47 | -0.45 |
| Solenoidal, T | - 3.64 | - 3.35 |

- Vl.Kashikin

- K.Yonehara