Thoughts on C0 IR Design Study -- Plan #1

Peter H. Garbincius

May 15, 2002

# Plan #1: Reuse IR Components from B0 and/or D0 after CDF/D0 Complete

At this time, we do not have a fully developed plan to be able to
provide the adequate luminosity for BTeV (2 x 10^32^) with separated
orbits, injection, and squeeze. IR components could be taken from either
CDF or D0 or from both. It would seem to me that the initial design
would be to leave an IR at either CDF or D0 and swap the Collins
straight section from C0 with the other of these now existing IR's. This
would allow the ½ integer tune in both planes associated with the IR to
also move with the elements to C0. If this can't be accomplished, then
there might be more complications in also trying to inventory and use
existing spares.

The general idea is to not have to build any magnetic components.
However, there likely would be new components for or modifications to
the cryogenic power feeds, spools, and bypasses, and major modification
to the installation of the magnet power systems.

There may be a further complication relating to swapping the 72" powered
spool pieces. The existing spools at B0, C0, and D0 not only contain the
tune matching quads, but also an array of other trim or vernier magnets
such as h-dipoles, v-dipoles, skew quads, sextupoles, etc. I have not
done any more than list those existing elements in the companion
spreadsheet (as specified on v3h15av2_collide.print). I ask the
BD/Tevatron group to start looking these over and try to figure out if
any direct swaps are acceptable, or whether some of this trim
capacity/flexibility can be reduced. (I realize that Bob Kephart has
requested Ray Hanft to investigate this, but I'm sure the trim
specifications will ultimately have to be with the Tevatron Department.)

**PHG First Attempt at a C0 IR Design under Plan #1**

In preparation for the April 2002 PAC meeting which considered
re-endorsement of the BTeV proposal, I did the absolutely simplest,
non-radical beam reconfiguration that one could consider.

> I assumed that the Collins straight could be moved from C0 to B0 or D0
> and the
>
> IR from B0/D0 moved to C0.
>
> I assumed that the C0 could be treated as an insertion between B42 and
> C18 with
>
> constraints to the lattice parameters given by v3h15av2_collide.print.
>
> This is likely an incorrect assumption since there are NO adjustable
>
> strong correctors in the Collins straight and those published lattice
>
> functions may not be so easily attainable at B42 and C18.
>
> I did not look into the possible variation in trim/vernier
> capabilities and BPM
>
> placements for the 72" spools as mentioned above.

Since BTeV requires more space within the inner quadrupoles than CDF/D0,

I looked at a simple doublet focus (compared to the CDF/D0 triplets)

where the outer Q2 quads (132") and the adjacent power feedcan remained

in the exact CDF/D0 configuration with respect to the IP, the longer Q3

quads (232") were removed, and the Q4 quads (132") had the beginning of

their magnetic field region placed at 12.452 meters. Including the
inboard

end cans on the Q2 quads, this gave BTeV [+]{.underline} 40 feet from
the IP for their

experiment. The would definitely be a need for new length powered spool

pieces between the Q2's and the Q4's.

Taking this simple configuration, I was able to find a matched,
dispersion-free

(η = 0, η' = 0) waist (α = 0) at C0 with β\* = 1.5 meters. The β\* could
not

be lowered below 1.5 meters without overpowering some of the strong

corrector tune matching quads.

Scaling the expected Luminosity using the parameters and form factors
discussed

> Mike Martens and Peter Bagley's TeV Note 198 (1998) which gives CDF/D0
> a maximum luminosity of 5 x 10^32^, BTeV would get about 1/3 of that
> luminosity, or 1.67 x 10^32^, or \> 80% of their request for a
> crossing half-angle of [+]{.underline} 170 μrad in each plane.

However, with only a little bit of work, I was not able to find a simple
retuning of

> this C0 IR to match the injection orbit at B42 and C18
> (v3h01v2_inject.print) with β~max~ \< 225 meters in the doublet quads.

Neither have I looked at all at separated orbits nor low β squeeze.

The continuation of these studies for the simplified doublet tune will
doubtless

require globally fitting at least from A42 through D18 to take into
account

the Collins straight section moved to either CDF or D0.

Maybe a better approach would be to investigate **more imaginative, more
radical** rearrangements of the Tevatron configuration between B42 and
C18.

The EXCEL file c0ir_interchange_b0-d0.xls of the existing IR components
near B0, C0, and D0 has six pages arranged in a way to facilitate
comparisons B0/C0/D0

Page 1 : B42 -- C0 Page 3: A42 -- B0 Page 5 : C48 -- D0

Page 2 : C0 -- C18 Page 4 : B0 -- B18 Page 6 : D0 -- D18