# Presentation: 617733

## Accelerator Physics

**Samuel Krinsky**
**NSLS-II ASAC Meeting**
**July 17-18, 2008**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Accelerator Physics Group

- A. Blednykh, J. Bengtsson, W. Guo, S. Kramer, Y. Li, B. Nash, I. Pinayev, T. Shaftan,  L.H. Yu

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Outline

**NSLS-II Parameters**
**Dynamic Aperture with Damping Wigglers**
**Higher-Order Multipole Tolerances**
**Touschek Lifetime**
**Collective Effects**
**Top-Off Safety Analysis**
**Summary**** **

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## NSLS-II Parameters

| Energy                                        3.0 GeV
Circumference                          792 m
Number of Periods                    30 DBA
Length Long Straights             6.6 & 9.3m
Emittance (h,v)                 <1nm, 0.008nm
Momentum Compaction           .00037
Dipole Bend Radius                   25m
Energy Loss per Turn              <2MeV | Energy Spread                     0.094%
RF Frequency                     500 MHz
Harmonic Number               1320
RF Bucket Height                >2.5%
RMS Bunch Length             15ps
Average Current                  500ma
Current per Bunch               0.5ma
Charge per Bunch               1.2nC
Touschek Lifetime                >3hrs |
| --- | --- |

**NSLS-II ****Parameters**

**Refinement of SR lattice design continues but is**
**restricted to not impact conventional construction**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Lattice Functions for One Cell

- Long ID

- Short ID

- Dispersion
- Region

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Lattice Functions for One Cell

**Lattice Functions for One Cell**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Tune Footprint for Modified Working Point

**Tune Footprint for Modified Working Point**

- Bengtsson

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Frequency Map with DWs for Modified Working Point 

**Frequency Map with DWs for Modified Working Point**** **

- Bengtsson

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Sources of Systematic and Random Multipole Errors

- For ideal, symmetric magnets, higher order multipoles consistent with symmetry (“allowed multipoles”):    N(2m+1), m=0,1,2,...
-     dipole: 1,3,5,7, ...
-     quadrupole: 2, 6, 10, 14, ...
-     sextupole: 3, 9, 15, 21, ...
- Random Errors from manufacturing tolerances

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Normalized Systematic Multipole Errors

|       x 104 | NSLS-II regular | NSLS-II 
High Precision | SOLEIL | CELLS | SLS |
| --- | --- | --- | --- | --- | --- |
| B26 | 1 | 1 | 1 | 2 | 1.1 |
| B210 | 3.3 | 0.5 | 0.2 | 4 | -2.5 |
| B214 | 3.5 | 0.1 | 0.1 |  |  |
| B39 | 1 | 0.5 | -1 | 5 | -2 |
| B315 | 1 | 0.5 | -0.5 | 7 | 6.9 |
| B321 | 4 | 0.5 |  |  |  |

**Ratio ****(x10****4****)**** of multipole field to design quadrupole or sextupole field at reference radius: R = 25 mm**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Dynamic Aperture

- No Multipole Errors

- Original Tolerances

- New Tolerances

**Dynamic Aperture**

- Systematic multipole errors reduce
- the dynamic aperture for negative
- momentum deviation

- Guo & Nash

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Scattering at 

- Scattering at
- High Dispersion

- Scattering at
- Low Dispersion

**Energy Acceptance Depends on Location of Scattering**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Local Touschek Loss Rate Without Landau Cavity

**Tau = 3.3 hrs**

**Tau = 2.3 hrs**

**1/tau(s) (1/hr)**

**1/tau(s) (1/hr)**

**S (m)**

**S (m)**

**Local Touschek Loss Rate Without Landau Cavity**

- δacc

- δacc

- Long ID

- Short ID

- Long ID

- Dispersion
- Region

- Dispersion
- Region

**S (m)**

**S (m)**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Collective Effects

- We have estimated instability thresholds based on an impedance budget suggested by experience at ESRF and APS.
- We are calculating the impedance of the NSLS-II components using GdFidL. Calculated results obtained thus far lie within the budget.
- Calculations are first performed using a 3 mm Gaussian bunch.  Next we plan to calculate the wakefield for a 0.5mm bunch for use as a pseudo Green’s function for tracking simulations.
- In order to carry out the GdFidL calculations for a 0.5mm bunch, we require improvements in the code (W. Bruns) and increased computing power (upgrade of our cluster).
- Single bunch (0.5 mA) and average current (500 mA) goals are achievable

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Detailed Calculated Impedance (s = 3mm)

| Object | Num.  of occur. | 
V/pC | (ImZ||/n)0
 | 
V/pC/m | 
V/pC/m |
| --- | --- | --- | --- | --- | --- |
| Stick Absorber (Horizontal) | 180 | 3.4x10-3 | 9.2x10-6 | 0.5 | 0.002 |
| Absorber (Vertical)  | TBD | TBD | TBD | TBD | TBD |
| Flange Absorber | TBD | TBD | TBD | TBD | TBD |
| Elliptical Bellows | 180 | 10x10-3 | 37x10-6 | TBD | TBD |
| Circular Bellows | TBD | TBD | TBD | TBD | TBD |
| Regular BPM                                       | 200 | 24x10-3   | 47x10-6 | 0.9 | 1.1 |
| ID BPM | 40 | 6x10-3 | TBD | TBD | TBD |
| Cavity transitions/straight     | 2 | 3.5 | 14x10-3 | 25.4 | 57 |
| 500MHz CESR-B cavity         | 4 | 0.31 | - | 0.17 | 0.17 |
| 1500 MHz CESR-B cavity      | 4 | 0.52 | - | 2.6 | 2.6 |
| Dipole Chamber | 60 | 3.3x10-5 | 0.7x10-7 | 4.5x10-3 | 0 |
| Multipole Chamber | 90 | 0.5x10-5 | 0.1x10-7 | 0.7x10-3 | 0 |
| Mid-IR chamber (25mm gap) | TBD | TBD | TBD | TBD | TBD |
| Far-IR chamber (78mm gap)                         | 4 | 84x10-3 | TBD | 5.1 | TBD |
| SCU chamber geometric        | TBD | 22.6x10-3 | 0.6x10-3 | 61 | 257 |
| SCU chamber ease* (2m) | TBD | 5.6x 10-3 |   | 13  | 26 |
| IVU geometric                    | TBD | 95x10-3 | 1.1x10-3 | 136 | 425 |
| IVU resistive wall (3m) | TBD | 66x10-3  |   | 112  | 225  |

*********0******=2************384.6 kHz***

***SM ******– simplified model***

***1 ******– Values were calculated by R. Nagaoka for SOLEIL with σ******s****** = 6 mm***

| Object | Num. of occur. | 
V/pC | (ImZ||/n)0
 | 
V/pC/m | 
V/pC/m |
| --- | --- | --- | --- | --- | --- |
| DW Chamber | 8 | TBD | TBD | TBD | TBD |
| Kickers Chamber | 1 | TBD | TBD | TBD | TBD |
| S4A chamber  | 30 | 1x10-3 | TBD | TBD | TBD |
| Injection Region | 1 | TBD |  TBD | TBD  | TBD  |
| Scraper (Horizontal)               | 2 | 0.22 | 1.4x10-3 | 22 | 2 |
| Scraper (Vertical) | 2 | TBD | TBD | TBD | TBD |
| Flange 1 | 300 | 0.47x10-3 | 16x10-6 | 0.141 | 0.141 |
| Vat valve  | 60 | 2.1x10-3 | TBD | TBD | TBD |

***Items in red calculated since***
***November DOE review***

- Blednykh

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

**Notes:**
The geometric wakefield and impedance produced by the components of the NSLS-II storage ring have been computed for an electron bunch length of 3mm rms
Our results for the loss factor, the imaginary part of the longitudinal impedance at low frequency divided by the revolution harmonic and the transverse kick factors are summarized in this table.
Here we are talking about the dipole kick factors, because dipole modes are main contributors to the transverse impedance.      
In many large high-energy machines, the resistive wall impedance is the dominant contribution. From these results we can see that 2 Cavity transitions are the dominant contribution for NSLS-II for the longitudinal case.  
Our special concern is the RF cavity transitions, the IR chamber and CPMU.

##  courtesy Bob Hettel (SLAC)

**X-Rays**

**Injected Beam**

**X-Rays**

**Stored Beam**

**Injected Beam**

- ACCIDENT

- Combination of
- Bad Steering
- Bad Lattice Settings (conspiracy of magnets)

**Stored Beam**

***Simulation is necessary!***

-  *courtesy Bob Hettel (SLAC)*

- Require Proof that injected beam cannot pass through beamline
- beyond safe point inside shielded area.

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Top-Off Safety Analysis

- Working group formed to address top-off safety
- Visitors from SSRL and ALS have provided us with tools they have developed for tracking analysis
- Lessons learned from APS, SSRL and ALS will guide our work
- NSLS-II storage ring and beamline apertures are being defined and their impact on top-off safety is being investigated
- List of errors is being compiled and will serve as input for safety analysis
- Diagnostics, interlocks, and apertures will be specified to assure top-off safety
- A definitive proof of top-off safety will be developed and documented for review

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Working Group / Visitors

-        **Top Off Safety Working Group**
- Samuel Krinsky  (Accelerator Physics Group Leader)
- Robert Casey  (ES&H)
- P.K. Job (Radiation Safety)
- Timur Shaftan (Leader of Injection Systems Design)
- Sushil Sharma (Mech. Engineering Group Leader)
- Yongjun Li (Accelerator Physicist--Tracking Analysis)
- We have been meeting since February to begin discussion of top off safety issues

**    ****VISITORS**
-    Bob Hettel (SSRL) — April 4
-   Dave Robin (ALS) — April 29
-   Hiroshi Nishimura (ALS) — May 6-15
-      -- installed backtracking code for our use
-   Andrei Terebilo (SSRL) — June 2-6
-      --installed forward tracking code for our use

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Long ID Beam Line

- Fixed mask

- Safety shutter

- MID POINT
- OF LONG ID

- crotch absorber

- Apertures define
- beamline acceptance

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## 1mrad Beam Line Acceptance--OK

**Backward Tracking--Nishimura**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## 3mrad Beam Line Acceptance--Requires Extra Aperture

**Backward Tracking--Nishimura**

**3mrad Beam Line Acceptance--Requires Extra Aperture**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## 3mrad Beam Line Acceptance--OK with Extra Aperture

- Extra outboard aperture here

**Backward Tracking--Nishimura**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## 3mrad Beam Line Acceptance--Requires Extra Aperture

- Crotch absorber

- Fixed mask

- Safety shutter

**Forward Tracking--Terebilo**

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008

## Summary

-  Maintaining dynamic aperture for negative energy deviation required tightening the tolerances on the higher-order multipoles in the quadrupoles and sextupoles at large dispersion locations
-  Recent analysis of the Touschek lifetime suggests that achieving an energy acceptance for scattered particles of 2.5% in the low dispersion regions and 1.5% in the high dispersion regions will be sufficient to give a Touschek lifetime > 3 hrs with Landau cavity.  This is more relaxed than earlier estimates.  Optimization of DA with DWs continues.
-  Calculations of the impedance of the storage ring components is continuing---strong interaction with vacuum engineering and diagnostics development.
-  H. Nishimura (LBL) and A. Terebilo (SLAC) have installed their top-off safety analysis programs at BNL.  We are now beginning to use these codes to analyze top-off safety for NSLS-II.  One of our key goals is to determine as soon as possible what additional apertures are required to simplify achieving top-off safety.

- S. Krinsky    Accel Phys    NSLS-II ASAC Meeting     July17-18, 2008