Minutes of the MuCool metting, Oct 23, 1:30 P.M. - 3:30 P.M.

The meeting was held in the 10th Phys. Conf. room.

Present, at Fermilab : Dave carey, Steve Geer, Alvin Tollestrup, Dave
Finley, Tom Kobilarcik, Panagiotis Spentzrouris, yuriy Pischalnikov , 
Paul Lebrun, Dan Kaplan, Edgar Black, Zubas Qian, Al Russell, Mark Champion, Al
moretti, Dave Neuffer, Norbert HoltKamp
Over phone lines, Steve Kahn (BNL) and Kevin Lee (UCLA). 
Sribe is Paul Lebrun.

I. Discussion on the potential risks at the ongoing R&D programs
on our r.f. development.  (Norbert HoltKamp)

Norbert expressed concerns about our program on the use of high gradient,
pillbox type cavities, with 5 mill Beryllium windows.  
    
   a. This R&D will take time, for instance, the current plan is to
   start high power test a year from now.  (Meanwhile, we plan to assemble the
   low power 3-cell cavity at Lab G, only 3 Beryllium windows have been 
   ordered. ==> Should we try to speed some elementary, but high power test
   sooner? 
   b. What happens when Beryllium windows fails?  This can not mean the end 
   of this R&D program, we must have backup plans.  Note that there are many
   reasons why such windows may fail : breakdonw, discharge, e- emissions, 
   excessive outgassing, behavior while multipactoring.. 
   
   => Towards an aggressive test of high gradient field on thin Beryllium 
   windows, even if the windows are smaller, and at a different frequency.
   => Based on simulation, think about a fallback position. 
   
Dan Kaplan raised the issue "Should we consider using a grid rather than a 
foil"
Norbert and Al answered that many things change, it is not obvious that it is
better. Note also that this is a setup which is definitly more complicated
to simulate on the computer. The idea is interesting, but far from an obvious
winner. 

So what should happen between "now" and two years from now...  Helen Edwards,
Alvin and Norbert, during a luncheon conversation, considered studying smaller
Beryllium foils, with surface fields of 35 MV, in an existing r.f. gun, at A0.
Note that we could use thinner Beryllium windows, to compensate for the
different radii (mechanical breakdown under stress will depend on radius and
thickness, but we can play!).  We need to assemble a little bit of r.f.
hardware (couplers, wave guides..) but all this equipment exists. We also need
to order small Beryllium foils to braze to a support that can be inserted in
the gun.  Lastly, we need to schedule the installation of this equipment at A0,
or  at least most of it, before December, so that when we received the
buttons,  we are ready.  Note that Helen's group plans to use the A0 pit for
their experiment, but Mark Champion voiced the opinions that there might be 
opportunities to share the resources (e.g., they won't run all the time..)

Norbert wants a budget code, and a blessing to "steal" what we need.    
No dissenting opinions were voiced on the overall merits of the plans, 
$$ might be a problem. Also we need young people that can do things, we'll need
to staff the little A0 lab. (Editor's note: Quit pickin on us "old" guys!)

The second approach is to attempt to design an Alternate Solenoid Cooling 
channel based on conventional cavities, with open iris. Paul Lebrun 
is studying the problem, and is hopefull that a slightly shorter LH2 abosrber,
combined with a slight difference in phase will provide a cooling channel with
equivalent performance. The required peak voltage will be around 30 MV, 
definitly greater 26 MV.  This assumes running with an identical lattice and at
the same momentum (186 MeV), and starting with the same 6D emittance. 

These results are encouraging. We were hoping to get improved performance due
to the more homogenous field, but a simple calculation by Alvin, backed by 
results from DPGeant showed that this is not true. But even so,
removal of the Beryllium foils, and the absence of multiple scattering, 
may make the difference. 

However, these simulations were done with 2pi/4 structure, unphysical if we 
have a
standing wave with open irises => got to go to 2pi/3, pi mode. => less 
phase stability! => back to simulation!. Both Superfish and DPGeant. I take 
that back, before we spend time on Superfish sim., I better run DPGeant 
with 2pi/3 or pi mode, to check if we have enough longitudinal focusing. 
 Issue: can we have a stable 2pi/3 mode with standing wave? Do we have to 
 resurrect the issue of traveling wave vs standing wave?

II. Status of the low power cavity development - Al Moretti 

Drawings of the 3 and 1/2 half cell, featuring two beryllium windows, 5 mill, 
16 cm. diameter have been presented. The cavity itself is currently being
machined at Univ. of Mississippi, they are 10% done, and the schedule 
for completion is the end
of November. The Beryllium window and support ring should be available in 
mid-December.   
Al also showed the location of this setup, including power supply, pulse 
shaping network, klystron and the cavity itself on the lab G floor plan.
Overall safety issue were raised.  Two divisions are involved, as sposkesman,
Steve Geer has this responsibility, and therefore will have a leading role in
the supervision of all safety matters.  This involves engineering know-how and
bureaucracy.
Meanwhile, there is still some cleanup to do in lab G, in particular magnet
disassembly.  It's the responsibility of PPD.  One mechnical engineer and two
techs will be dispatched, this will take of the order of two weeks. Also,
Al has requested some drafting help to get a professional floor plan for 
this new Lab G.  
We also briefly discussed the future location of Li Lens development. It looks
like we are already running out of room in Lab G, however, there is one addtion
to the building.  But we were told this addition is slated for demolition (or
intense remodeling). We should get organized on that front as well...     
	
III Status of MUCOOL/Geant simulation at UCLA, Kevin Lee.

Kevin is making progress at getting familiar with the code. He still has
some difficulty compiling and linking Geant v3.21, without Patchy, but he'll get
there.

IV Status of MUCOOL simulation and reconstruction, BNL, Steve Kahn.

Steve reported on recent progress towards a simulation/reconstruction package 
capable of measuring the momentum of the muons.  Since the muon paths are quite 
convoluted, conventional methods for reconstruction and track fitting don't
apply. At least, we do not have a pattern recognition problem ( assuming that
the TPC's are not noisy, in the environment where they have to run!). 
Steve is currently trying to find a procedure to get a first order measurement
of the momentum, by noticing that (i) in the straight solenoid, the TPC 
measures
a set of points, x,y and time coordinate. two such points can give a crude
estimatre of the radius and the phase advance. (ii) in the bent solenoid, 
the point after the bend has drifted vertically due to a difference between the
muon momentum and the reference momentum => Can we iterate based, and converge
towards a stable momentum value? 
This is only our first attempt at such a fit. Steve showed correlation plots,
demonstrating that indeed points drift the right way in the bend solenoid. 

V Status on the design of the LH2 absorbers. Dan Kaplan.

Dan reviewed two proposals to achieve cooling (the power dissipation is 500
Watt). These two different designs are: 
1. External cooling loop.  See for instance the Bates Sample target.  
2. A Heat exchanger inside the solenoid surrounding the "closed" LH2 vessel.

The first design is conventional and conservative, but takes room around the 15
Tesla solenoid...

The second design is difficult. Mike McAshan thinks it is in fact hopeless. 
The natural convection inside the vessel will be insufficient to maintain the 
small Delta.  Without it, we will get of the order of 10% density variation.
Forced convection (stirring inside the vessel), is mechanically (and
electrically) very hard to implement.. 
Note the delta T is computed ignoring the fact that LH2 is diamagnetic, 
and levitates at 5 Tesla..

But, we think we have enough room in the system for the external cooling loop. 
Dan showed an update of Ed Black's drawing, showing the location of the pump 
and heat exchanger. 

Dan also raised the issue of possibility of significant change of the 
properties
of LH2 due to the electric field  created by the space charge, due to the
intense muon bunch. However, the field is too small, moreover, such beams 
were dumped in such targets before... 

VI Final last news - Steve Geer

Steve reported on a phone conference we had on Thursday (Bob Palmer, Li Derun, 
Al Moretti, Alvin and I) The topic was the reconciliation of the 
radial extension of the high beta solenoid vs the r.f. cavity.  
Bob Palmer said he had a solution for the 2m. Alternate Solenoid, where the 
inside radius of the coils was at 23 cm.  Since the r.f. cavity outer radius is
21 cm, this leaves less than 2 cm for cryostat.( And we need one, since it has
been decided that we will run the cavity at room temperature. ) 
Bob will send his new field map to the magnet dudes down South, and the coil or 
current sheets to Icool and DPGeant expert for verification.