Overview and issues of the meic interaction region
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Overview and Issues of the MEIC Interaction Region. M. Sullivan MEIC Accelerator Design Review September 15-16, 2010. Interaction Region Design Concerns Accelerator Concerns Detector Concerns MEIC IR and detector Summary. Outline.

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Overview and issues of the meic interaction region

Overview and Issues of the MEIC Interaction Region

M. Sullivan

MEIC Accelerator Design Review

September 15-16, 2010


Outline

Interaction Region Design Concerns

Accelerator Concerns

Detector Concerns

MEIC IR and detector

Summary

Outline


Interaction region design

There are several conflicting constraints that must be balanced in the design of an Interaction Region

The design must accommodate the requirements of the detector in order to maximize the physics obtained from the accelerator

At the same time, the design must try to maximize accelerator performance which usually means having the final focusing elements in as close as possible to the collision point (minimize L*)

Interaction Region Design


Interaction region design 2

Beam related detector backgrounds must be carefully analyzed and mitigation schemes developed that allow the detector to pull out the physics

For electron (positron) beams this means controlling synchrotron radiation backgrounds and lost beam particles

For proton (ion) beams this means primarily controlling the lost beam particles

Interaction Region Design (2)


Interaction region design 3

An adequate beam-stay-clear must be defined

If possible, the definition should permit beam injection while the detector is taking data (for the electron beam)

Modern light sources, the B-factories and (of course) the super B-factory designs use continuous injection

Machine performance with continuous injection is vastly improved

Interaction Region Design (3)


Interaction region design 4

The detector acceptance for the physics is a very important constraint

Usually all detectors want 4 solid angle coverage

This wish has to be tempered with the needs of the accelerator and the requirements of the final focusing elements

Interaction Region Design (4)


Meic interaction region design

The MEIC Interaction Region Features

50 mrad crossing angle

Detector is aligned along the electron beam line

Electron FF magnets start/stop 3.5 m from the IP

Proton/ion FF magnets start/stop 7 m from the IP

MEIC Interaction Region Design


Table of parameters electrons

Electron beam

Energy range 3-11 GeV

Beam-stay-clear 12 beam sigmas

Emittance (x/y) (1.02/0.20) nm-rad

Betas

x* = 100 cmx max = 435 m

y* = 2 cmy max = 640 m

Final focus magnets

NameZ of face L (m) k G (11 GeV)

QFF1 3.5 0.5-1.7106-62.765

QFF2 4.2 0.5 1.7930 65.789

QFFL 6.7 0.5-0.6981-25.615

Table of Parameters (electrons)


Table of parameters proton ion

Proton/ion beam

Energy range 20-60 GeV

Beam-stay-clear 12 beam sigmas

Emittance (x/y) (2.25/0.45) nm-rad

Betas

x* = 100 cmx max = 2195 m

y* = 2 cmy max = 2580 m

Final focus magnets

NameZ of face L (m) k G (11 GeV)

QFF1 3.5 0.5-1.7106-62.765

QFF2 4.2 0.5 1.7930 65.789

QFFL 6.7 0.5-0.6981-25.615

Table of Parameters (proton/ion)


Interaction region and detector

Ultra forward

hadron detection

Small angle

hadron detection

Central detector with endcaps

Low-Q2

electron detection

ion quads

dipole

Large aperture

electron quads

IP

dipole

dipole

Small diameter

electron quads

~50 mrad crossing

Solenoid yoke + Muon Detector

Solenoid yoke + Hadronic Calorimeter

RICH

Tracking

RICH

Muon Detector

EM Calorimeter

EM Calorimeter

Hadron Calorimeter

HTCC

Interaction Region and Detector

Courtesy

Pawel Nadel-Tournski and Alex Bogacz

5 m solenoid


Estimate of the detector magnetic field b z

4

3

Tesla

2

1

QFFP

QFFP

QFFL

QFF2

QFF1

QFF1

QFF2

QFFL

~2 kG

Estimate of the detector magnetic field (Bz)

The detector magnetic field will have a significant impact on the beams. Some of the final focusing elements will have to work in this field.


Energy range

Both beam energies have a fairly large energy range requirement

The final focus elements must be able to accommodate these energy ranges

An attractive alternative for some of the final focusing elements (especially the electron elements) is to use permanent magnets – they have a very small size and do not need power leads

However, any PM design has to be able to span the energy range

Energy range


First look at backgrounds

First look at backgrounds

50 mrad

Synchrotron radiation photons incident on various surfaces from the last 4 electron quads

38

P+

8.5x105

2.5W

4.6x104

240

2

e-

3080

Rate per bunch incident on the surface > 10 keV

X

Beam current = 2.32 A 2.9x1010 particles/bunch

Rate per bunch incident on the detector beam pipe assuming 1% reflection coefficient and solid angle acceptance of 4.4 %

Z

M. Sullivan

July 20, 2010

F$JLAB_E_3_5M_1A


Backgrounds

Initial look at synchrotron radiation indicate that this background should not be a problem

Need to look at lost particle backgrounds for both beams

Generally one can restrict the study to the region upstream of the IP before the last bend magnet

A high quality vacuum in this region is sometimes enough

Backgrounds


Summary

The IR is one of the more difficult regions to design

There are multiple constraints, however, balancing the various requirements to maximize the physics should be the primary goal of any design

The MEIC IR design shows good promise and initial studies of SR backgrounds show that this background looks ok

Summary


Conclusion

The MEIC IR design has tried to accommodate the requirements of the detector and the requirements of the accelerator

The design has benefited from input from both the accelerator and the detector community

A reasonable compromise has been struck and the design can deliver the needed accelerator performance while allowing the detector to collect the important physics

Conclusion


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