# Presentation: 108847

## AP issues in the IR upgrade

- Tanaji Sen
- FNAL

## Baseline Layout

- Quadrupoles first followed by separation dipoles
- Beams go off-axis in the quadrupoles
- Correction algorithm acts on both beams
- 16 long-range interactions on either side of IP

- LARP Meeting 9/16/03

- T. Sen

## Baseline Optics and Upgrade

- β* = 50cm, βmax = 5 km
- Hor. crossing angle at one high luminosity IP, vertical at the other
- Zero dispersion within the straight.
- -----------------------------------
- Upgrade: larger apertures, same gradients
- β* = 16cm, βmax = 15 km

- LARP Meeting 9/16/03

- T. Sen

## Separation Dipoles First

- Pros
- Reduces long-range interactions 3 fold
- Independent nonlinear correction for each beam
- Cons
- Larger β* for the same βmax
- Higher energy deposition in D1 from charged particles

- LARP Meeting 9/16/03

- T. Sen

## Quads between D1 and D2

- Pros
- Early beam separation reduces number of parasitics.
- Quads closer to the IP allows lower β* for the same βmax than Option 2.
-  Cons
- Dual bore quads with non-parallel axes. Magnet and AP issues.
- Large energy deposition in D1.

- LARP Meeting 9/16/03

- T. Sen

## Large X-angle: dipole first

- Pros
- Simplest layout for large crossing angle (±3.7 mrad)
- Allows lower β* for the same βmax than Options 2 and 3.
- Cons
- D1 suffers greater radiation damage than in previous options from neutral particles.

- LARP Meeting 9/16/03

- T. Sen

## Large X-angle: quads first

- Pros
- Allows the lowest β* for the same βmax .
- Cons
- Dual bore quads with non-parallel axes. Magnet and AP issues.
- Large energy deposition in D1.

- LARP Meeting 9/16/03

- T. Sen

## IR Parameters

- LARP Meeting 9/16/03

- T. Sen

## AP issues related to the IR

- Gradients and apertures of magnets
- Orbit and coupling correction within the IR
- Nonlinear correction with small and large crossing angles.
- Linear and nonlinear chromaticity correction (for larger βmax )
- Dynamic aperture (single beam) for different layouts
- Sensitivity to gradient and alignment errors
- Constraints on IR layout from injection optics
- Backgrounds in the IRs and Energy deposition
-             e.g synchrotron radiation with large crossing angles
- Beam-beam effects
-          long-range perhaps not an issue with early separation
- Impact of super-bunches – yes!

- LARP Meeting 9/16/03

- T. Sen

## Any requirements from detector backgrounds?

**Any requirements from detector backgrounds?**

- LARP Meeting 9/16/03

- T. Sen

## Non-parallel axes

-     Dual aperture quads

- Novel engineering to match magnet axes with beam axes.
- Range of crossing angles is constrained. If θc,nom = 4mrad
-         3 mrad < θc < 5 mrad
-      if rpipe = 50mm, and Q3 is 50m from the IP.
- Physical aperture is sensitive to **longitudinal** and transverse alignments.
- Each quadrupole is different
-       => reduces sorting possibilities.

- LARP Meeting 9/16/03

- T. Sen

## Large crossing angles @ the beam-beam limit

- Feasible if beam current is not limited by other effects, e.g. electron cloud, instabilities.
- At a half crossing angle = 4 mrad
-     beam separation in drift space (6 ints.)
-              Baseline       Option 4
-          (β*=0.5m)        (β*=0.15m)
-          d = 9.5σ        d = 138σ

- 4 mrad

- 20 mm

-       L = 5m

-  => Long-range not an issue
-     => same crossing plane at both IPs

-   Large feed-downs if beam axes not matched to magnet axes. If average offset =10mm        and b10  =  0.1  => feed-down multipoles from b10 alone are,

-  b9 = 0.6, b8 = 1.6, b7 = 2.4, b6 = 2.5, b5 = 1.8, b4 = 0.9, b3 = 0.3, b2 =  0.06

- LARP Meeting 9/16/03

- T. Sen

## Correction for baseline optics

- LARP Meeting 9/16/03

- T. Sen

## Corrector Layout for baseline optics

- LARP Meeting 9/16/03

- T. Sen

## Nonlinear correction: baseline 

- LARP Meeting 9/16/03

- T. Sen

## Slide 16

- LARP Meeting 9/16/03

- T. Sen

## Slide 17

- LARP Meeting 9/16/03

- T. Sen

## HERA Luminosity Upgrade

- Path to higher luminosity
-     - e quads moved closer to IP
-        from 5.8m to 2m
-     - p quads moved from 28m to
-       11m
-      - earlier separation with SC
-       dipoles partially in detector
-      - stronger focusing in e-ring
- Specific Luminosity close to design
- Detector backgrounds (mainly synchrotron radiation) a major problem

- IR Layout after upgrade

- LARP Meeting 9/16/03

- T. Sen

## CESR IR Upgrade

- Implemented in 2001
-  Phase III insertion region within ±2.55 m of IP.
-      First quad (permanent magnet) at 0.34m from IP
- βy* reduced from 18mm to (13 – 7) mm.
- Parasitics every 2.1m
-     Betas at parasitics in IR same as in the arcs.
- SC rf allowed bunch length reduction from 19mm to 13mm

- Henderson CBN 99-28

- LARP Meeting 9/16/03

- T. Sen

## PEP-II IR Upgrade

- Planned for 2005
- 1st focusing quad will be moved closer to IP effectively by 0.2m to lower βy* to 5mm from 11-13mm.
- Requires shorter bunch lengths
- Introduce a 3.25mrad crossing angle – earlier separation
- Lower long-range tune shifts may allow more bunches (1 in each bucket).

- Sullivan PAC03

- LARP Meeting 9/16/03

- T. Sen