Accelerator Physics

1 BROOKHAVEN SCIENCE ASSOCIATES

Accelerator Physics

Samuel KrinskyNSLS-II Accelerator Physics Group Leader

NSLS-II Accelerator Systems Advisory Committee February 1-2, 2012


Outline

• Accelerator Physics Group

• Progress

• Conclusions


Accelerator Physics Group

G. Bassi, J. Bengtsson, A. Blednykh, W. Cheng, J. Choi,

W. Guo, P. Illinski, S. Kramer, Y. Li,

I. Pinayev (CAD), L. Yang, L.H. Yu

Y. Hidaka, B. Podobedov, S. Seletskiy, X. Yang


Interface with Engineering Groups

Magnet Design: J. Bengtsson, W. Guo, Y. Li, Diagnostics: A. Blednykh, W. Cheng, P. Ilinski, I. Pinayev, S. SeletskiyControls: J. Choi, Y. Hidaka, L. Yang, L.H. Yu, Insertion Device: J. Bengtsson, O. Chubar (ESD), W. Guo, Safety: S. Kramer, Y. LiVacuum: A. Blednykh, IlinskiRF: A. Blednykh, G. Bassi


Technical Progress Analysis of field tolerances for ring magnet acceptance

Studies of lattice flexibility: reduced symmetry, specialized insertions

Calculation of Impedance of components• DESY 7-Cell Cavity OK for early commissioning goal of 25ma

Development of parallel computer code to simulate coupled bunch instabilities including long and short range wakefields

Equipment Protection System Maturing• Without IDs—passively safe to 50ma

Development of high level application programs• Review in April 2012


Technical Progress (cont.) Commissioning Planning

• Draft report, HLA software, Focus for Accel. Phys. Group Meetings Beam Loss Control Monitoring System

• Review in July 2011 Top-Off safety• Review in July 2011, March 2012, Fall 2012 X-ray diagnostic beamlines and visible light monitor

• Review in July 2010, X-ray BPMs

Transverse feedback system

Insertion devices beyond baseline • Review in January 2012


Physics input to the magnet production-1

• Trend study of the field quality, and make suggestions on shimming.• Monitor the field quality of all the magnets before approving the shipment.

B5 (normal 10 pole) of Danfysik sextupoles has a large current dependence. They will be used for several families with a large current span. We suggest them to shim the magnets at 60% of the full strength, rather than 100%; therefore the beam dynamics effects will be cancelled among families.

10-pole

14-pole

IHEP tune the harmonics by replacing the ironpins with stainless steel pins. The magnetsfrom production have a large b5 (4-8 units), afterpinning, b7 grows to ~ 2 units. We suggest themretract the two movable center poles by 20-40 μm.


Physics input to the magnet production-2• Identified the design defects in the skew quadrupole coils, and proposed a solution.

• Analyze the dipole field mapping data, and determine the nose piece parameters.

+

+

--

--

x

y

0 .3 0 .2 0 .1 0 .1 0 .2 0 .3

0 .03

0 .02

0 .01

0 .01

0 .02

0 .3 0 .2 0.1 0 .1 0.2 0.3

0.02

0.04

0.06

0.08

z

z

A4=1000 units, equivalent to ~15 units in a normal quad. We use a four-current model, and calculatedthe a4 component from the present dimension (center plot). If the dimension is symmetrized, the integratedstrength becomes negligible. The conclusion is verified by a more advanced tool.

A4 A4

Name Nose θ /100(mr)

L(m)

∫b1*102 Left

∫b2 *104

Left

35mm SN01

no 9.7996 2.44227 1.90 6.7

35mmSN01

#2 nose 1.0367 2.60567 1.8 6.15

90mmSN01

no 1.0409 2.62573 1.9 1.69

The goal is to match the two types of dipoles. We first track through the dipole field map for close-orbit, Then use polynomial fitting to obtain multipoles on the curved orbit. The integrated strength is compared In the table. The length and chamfering of the nose piece are determined from these parameters.


Compensating APPLE-II (EPU49) Dynamic Focusing Effects

by Current StripsAPPLE-II RADIA Model with Strips Idea: I. Blomqvist

Implementation at BESSY: J. Bahrdt

Verti

cal (

Equi

vale

nt)

Fie

ld In

tegr

al [G

.cm

]

Horizontal Position [mm]

Curre

nt [A

]

Horizontal Position [mm]

in Linear Vertical Polarization Mode

Equivalent Vertical Field Integrals from Dynamic Focusing and from the Current Strips

Compensating Currents in Lower Strips

Electron Trajectory in 3D Magnetic FieldWithout and With Correction

Horizontal Trajectory

Longitudinal Position [mm]

x0=0, y0=0 before Undulator

Vertical Trajectory

Horiz

. Pos

ition

[μm

]Ve

rtica

l Pos

ition

[μm

]

Horizontal Trajectoryx0= -4 mm, y0=0 before Undulator x0= 4 mm, y0=0 before Undulator


Horiz

onta

l Pos

ition

[μm

]


Horiz

onta

l Pos

ition

[μm

]

Efficient Solving for CurrentsUsing Least-Squares Linear Fit

QJI

Field Integral from Current Densities:

IQQQJ T1T )(

Current Densitiesfrom Field Integral:

Number of Strips used: 2 x 20Strip Dims: 2 mm x 0.3 mm x 2 mHorizontal Gap bw Strips: 1 mmVertical Gap bw Strips: 10.7 mmMax. Current obtained: ~ 2.3 AAPPLE-II Vertical Gap: 11.5 mm

)()( xx lowerupper JJ

Since the Dynamic Effectsare Anti-Symmetric vs X:

Matrix calculated using RADIA


High Level Application Programs Control system design provides independence of HLA from low-level details

MatLab middle layer will be available

In-house development will emphasize a python environment utilizing services being developed by controls group

The online calculation engine uses Tracy subroutines

Documentation including programing reference and user guide available on-line.


HLA Progress 1

1. Lattice (Magnet) mapping to channel access is done by Channel Finder Service (developed in Controls group)

2. High level magnet PV control is Object-Oriented. It uses CFS to control magnets in the same Group/Family/Girder/Cell/Symmetry or whoes name matching certain pattern. (done)

3. Low level control uses direct PV name in Python or control panels developed with Control System Studio (CSS). (contributed from HLA team, but relying on each subsystem)

4. Physics routines are in progress. Orbit Response Matrix (ORM) library is done. Twiss measurement, global orbit correction and local bump control are done. ( more routines after Jan-Feb series of AP talks)

5. Graphical User Interface(GUI) applications are in progress. Orbit display GUI is done. Beam Based Alignment (BBA) script version is done.

6. Linear Optics Modeling (LOCO) is in progress. (J. Choi)7. Misc: Data storage (Input/Output) related routines and unit conversion are in

progress.


HLA Progress 2

• Document including tutorial and examples for each routine/module are developed together with the code.

• Communications with Diagnostics group are well established on RF BPM data acquisition.

• Took advantages of tools from controls group. Raised requirements on CFS, CSS, archiver.


Beam Loss Control & Monitoring system

Beam apertures and scraper to localize the major beam losses

Verify the fraction of beam captured in shielded regions:using current monitors and beam loss monitors ( neutron and Cerenkov monitors)

Principle of scraper localization demonstrated in Xray ring

Thin scrapers provide high sensitivity local beam loss signal using Cerenkov detectors and reduced radiation off scraper

High dynamic range Cerenkov light detector system design to detect 0.1 pC/sec lifetime losses to Injection and beam dump losses of 3mC/sec


Demonstrated Loss Control in Xray Ring-1Xray Ring has 5mm Cu scraper near dispersion maximum in SP=3

0.91m CBLM in dipole end


Demonstrated Loss Control in Xray Ring-2

-40 -35 -30 -25 -20 -150

1000

2000

3000

4000

5000

6000

X15 Scan proCBLM Hi Gain

Lifetimex100CBLM*20 (mV)b2bm2 (raw)b1bm2 (raw)b1bm1 (raw)

X15 Inner Scraper Position [mm]

Life

time

hr*1

00],C

BLM

[mv*

20],B

LMs

BLM monitors decrease and CBLM increase showing change in beam loss locations by the scraper scan on the momentum apertureBeam loss at CBLM after scraper, charge loss rate used to calibrate CBLM

As the scraper reduces momentum aperture:

__ CBLM show increaseEven before the

__ LIFTIME starts decrease__ b2bm2 BLM1 decrease__ b1bm1 BLM2 decrease__ b1bm1 BLM1 decrease


Transverse BxB Feedback

16

• 500MHz digitizer received and tested using simulated pulse

• 10kHz-250MHz, 500W broadband amplifiers received and tested

• First stripline kicker assembled and tested

• Dedicated button BPMs free of trapped TE mode allocated

• Heliax cables purchased

EDM panel

iGp12


Visible SLM

• Streak camera and fast gated camera received and tested using ~ps pulse laser

• Visible diagnostic beamline and experiment room design finalized. Procurement on-going.• In flange type fixed mask, defines the 3mrad*7mrad

(H*V) radiation fan• Cold finger blocks the central +/- 0.5mrad x-ray• 4’’ diameter first mirror, Glidcop + optical quality coating,

water cooled• Experiment rooms• Various optical components

• Engineer design review Nov-2011


500MHz PETRA-III 7-Cell Structure

500MHz PETRA-III 7-cell structure

• Normal Conducting Structure w/o HOM’s - Dampers

0.860 14.7 55700

0.867 17.5 56800

0.869 56.1 58200

0.871 19.7 59400

1.043 83.6 40400

1.046 26.2 40900

1.089 17 49400

1.465 15.5 54600

1.545 26.8 44300

• Transverse Higher Order Modes

• Longitudinal Higher Order Modes

0.722 1.1 32200

0.728 3 33600

0.733 0.7 35000

0.738 0.5 35500

0.739 0.5 36000• Mode frequencies provided by R. Wanzenberg


Coupled-Bunch Stability Analysis (Iav=25mA)

• Longitudinally stable : Growth time . Damping time

• Transversely unstable at zero chromaticity (ξ=0): growth time

Cure: 1) Run at positive chromaticity to provide damping via slow head tail effect

2) Frequency shift (ΔΩ) of HOM’s

Self consistent simulations of head-tail effect + coupled-bunch interaction with the OASIS code

Fastest growing mode μ=74 Slow head-tail effect: damping at ξ=2

M=132, N=3.1x109, RBB =1MΩ/m: (1,60KHz), (2,40KHz) M=132, N=3.1x109, RBB=0.5MΩ/m : (1,110KHz), (2,70KHz) M=66, N=6.2x109, RBB=0.5MΩ/m : (1,60KHz), (2,40KHz)

Working Points (ξ,ΔΩ)

).(Re)/(4

)Im(100

0

px

b pMZeE

McI

vs. at

ΔΩ ,𝑘𝐻𝑧


Summary Results of Calculated Impedance (s=3mm) Number of occur. V/pC

(ImZ||/n) V/pC/m V/pC/m

Photon Absorbers

Multipole Stick ABS (20mm) 2 2.8x10-2 1.2x10-4 TBD TBD

Multipole Stick ABS. (22mm) 28 0.2 0.7x10-3 TBD TBD

Multipole Stick ABS (25mm) 96 0.2 7.7x10-4 TBD TBD

Dipole Crotch ABS (21mm) 60 0.2 0.9x10-3 TBD TBD

Flange ABS (64mmx21mm) 100 2.1 TBD 143 269

Bellows Regular Bellows (r=12.5mm) 200 4.4 1.2x10-2 TBD TBD

RF Bellows (r=120mm) 1 TBD TBD TBD TBD

Diagnostic Regular BPM (7mm, r=12.5mm) 180 1.62 4.1x10-3 90 90

ID BPM (4.8mm, r=5.75mm) 60 0.53 1.8x10-3 TBD TBD

Stripline Kicker (4e60, 15cm) 2 1 0.04 42 42

Vertical Kicker (2e90, 30cm) 1 0.4 0.04 22 23

Horiz. Kicker (2e90, 30cm) 1 TBD TBD 23 22

RF Cavity transitions/straight 2 7 28x10-3 50.8 114

500 MHz CESR-B cavity 4 1.24 ------- 0.68 0.68

1500 MHz CESR-B cavity 4 2.08 ------- 10.4 10.4

Scrapers Scraper (Horizontal) 3 0.44 2.8x10-3 44 4

Scraper (Vertical) 2 TBD TBD TBD TBD

Vat Valves Elliptical Vat Valve 60 0.54 TBD TBD TBD

RF1 Vat Valve (r=120mm) 2 0.08 TBD TBD TBD

RF2 Vat Valve (r=61.4mm) 1 TBD TBD TBD TBD

Number of occur. V/pC

(ImZ||/n) V/pC/m V/pC/m

Resistive wall 578.9m Al (VC, r=12.5mm) 1 6.3 --- 292 584

10m Al (Far-IR, r=23mm) 1 0.06 --- 0.8 1.6

45m Cu (IVU, r=2.5mm) 1 1.9 --- 2082 4164

43m StSt (S4, r=12.5mm) 1 2.1 --- 21.7 43.4

3.8m Inc (S4, r=12.5mm) 1 0.3 --- 12 24

56m Al (DW, r=5mm) 1 1.6 --- 442 884

15.6m Cu (Blw, r=14mm) 1 0.1 --- 4.1 8.2

14m StSt (Blw, r=13mm) 1 0.7 --- 30 60

15.5m StSt (3PW, r=12.5mm) 1 0.9 --- 43.5 87

10.2m Inc (Corr., r=12.5mm) 1 0.7 --- 32.5 65

loss x y loss x y

Vacuum Chambers

DW Chamber 8 0.16 TBD 128 456

Dipole Chamber 60 2x10-3 4.2x10-6 0.27 0

Multipole Chamber 90 4.5x10-4 9x10-7 0.06 0

Mid-IR Chamber TBD TBD TBD TBD TBD

Far-IR Chamber 4 0.34 2.8x10-3 20.4 TBD

Septum Chamber 1 6x10-3 TBD TBD TBD

S4 Stainless Steel Cham. 30 TBD TBD TBD TBD

IVU geom. (5mm gap) 15 0.46 TBD 1020 4350

EPU Chamber (10mm) 1 0.02 TBD 16 57


Conclusion

Accelerator physics progress includes:• A mature lattice design that meets the performance

requirements of NSLS-II• Incorporation of advanced IDs into lattice• Careful monitoring of magnetic field quality• Development of orbit feedback and bunch-to-bunch feedback

systems• Development of diagnostic beamlines• Study of collective effects—no show-stoppers.• HLA programs---using Python• Top-Off Safety and LCM Systems


Backup Slides


Technical Requirements & SpecificationsEnergy 3.0 GeVCircumference 792 mNumber of Periods 30 DBALength Long Straights 6.6 & 9.3mEmittance (h,v) <1nm, 0.008nmMomentum Compaction .00037Dipole Bend Radius 25mEnergy Loss per Turn <2MeV

Energy Spread 0.094%RF Frequency 500 MHzHarmonic Number 1320RF Bucket Height >2.5%RMS Bunch Length 15ps-30psAverage Current 500maCurrent per Bunch 0.5maCharge per Bunch 1.2nCTouschek Lifetime >3hrs


Lattice Functions for One Cell

Accelerator Physics

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