# Presentation: 802056

## 
LUMI and TUNE FEEDBACK

A. Ratti
LBNL

Presented at the DoE Review of the US LARP

Santa Rosa
2-4 Nov. 2005

_**LUMI and TUNE FEEDBACK**_
- A. Ratti
- LBNL
- Presented at the DoE Review of the US LARP
- Santa Rosa
- 2-4 Nov. 2005

***BNL - FNAL - LBNL - SLAC***

## Outline

- Systems description and progress report - Lumi and Tune Feedback
- Technical approach
- Progress since June
- Planning and Outstanding issues
- Program management
- Current issues and remedies
- Systems definitions, interfaces and responsibilities
- Integration of LARP and the LHC
- Conclusions

## LUMI - Requirements

- Help bring beams into collisions too

## LUMI - Specification

## LUMI - Conceptual DesignArgon Ionization Chamber

- I0

- 

-  = *x*GAP/*v*D

- Signal is proportional to the number of parallel gaps
- Capacitance add up with n. of gaps + slows down the signal
- Optimized for 6 gaps
- Must live in a radiation environment 100x worse than accelerator instruments have ever seen
- ~10Gy/yr, ~1018 N/cm2 over lifetime (20 yrs), ~1016 p/cm2 over lifetime

- V+

*x*GAP

- NGAP=2

## Ion Chamber Main Parameters

- Example shown (6 atm) is that of the upcoming RHIC experiment
- W. Turner - LBL-CBP TN 352, Oct. 2005

## Bunch-by-bunch Luminosity

*m*=0.33 INEL=80 mb SNR=5 2808 bunches

## Signal Processing

- Very low noise pre-amp in the tunnel
- Shaper section completes the analog signal processing
- ADCs integrated in a VME64 mezzanine card
- Interface defined by CERN BDI group

## LUMI Front-End Amplifiers: Cold Termination – Pavia Amplifier

- Original Design developed by P.F. Manfredi, L. Ratti and G.Traversi  of the University of Pavia using a cold termination technique:
*E. Gatti, P.F. Manfredi, IEEE Trans. Nucl. Sci, vol. NS 25, 1978, pages 66-74*

## 40 MHz Demonstration

- Tested the lumi detector at one of the hard x-ray beamlines at the ALS
- X-ray to ion pair production very hard to calculate
- White light configuration ~70-80 keV x-rays
- Chamber modification needed
- Tested proof of principle in August
- Complete set of data taken in September
- Required dedicated machine time to fill the ring with a 40 MHz bunch pattern
- Pattern used allowed for a gap to measure single bunch response
- Also tested without gap to see ‘continuous’ beam
- Enrico Bravin (CERN) at Berkeley during the experiments
- Allowed for much more integration efforts

## LUMI Experimental Setup at  ALS

- Built a dedicated part of the case in Aluminum
- Very thin (10 mils) wall exposed to the beam
- Had to add Cu foil to prevent saturation of the electronics

- New Al housing w. thin wall

## Beam hit the chamber from the side to allow for minimal attenuation

- ALS Beam Direction

- LUMI Experimental Setup at ALS

- LHC Beam Direction

## Raw Chamber Signal

- 20 ns/div

## After Pre-amp and Shaper

## 40 MHz Demonstration - Results

- Data recorded for multiple cases
- V scans
- Intensity scans (50 mA -> few mA)
- Multiple turns will give statistics
- Data analysis starting
- Already shown
- No space charge saturation effects
- Minimal pileup
- Greatly simplifies deconvolution
- Analysis underway
- Linearity, precision, dynamic range

## Last Major R&D Issue - Radiation hardness

- Planning a meaningful test of the materials is really hard: in most cases, test conditions are drastically different from LHC conditions
- Shower vs. neutrons
- Dose rate very different
- Parallel paths to minimize risk
- Careful research of materials properties
- Beam test at FNAL - if possible
- Fermilab is preparing a rad test facility at the p-bar target at the Tevatron is becoming available
- 120 GeV protons
- In collaboration with collimator group
- N. Mokhov is the FNAL contact
- LBL will prepare a plan by December 2005 for a test as soon as the facility is available in 2006

## Plans for a test in RHIC

- Install in IR 10
- Former experiment, now empty
- Goals
- Become familiar with operation in a hadron collider environment
- Benchmark device against the proven RHIC ZDC luminosity monitors
- Investigate some sources of background
- Develop signal processing implementation
- Integrate electronics in accelerator environment
- RHIC run 6 will have p-p and Au-Au
- Run planned for Jan. to ~Jun. 2006
- Multiple reasons to prefer Au-Au collisions
- More neutron yield
- Better neutron energy
- Dedicated collisions have less effect on lifetime than in p-p mode
- Beam-beam stronger in p-p

## RHIC Experiment Setup

## RHIC Experiment Planning

- Formal proposal ready for submission at the APEX meeting
- Nov 9-10, 2005
- Will ask for dedicated collisions
- May be able to run briefly in parasitic mode during the Au run
- Use the existing ZDCs in the interaction region
- Calibrate the luminometer with known device
- Learn about backgrounds
- Shipment of the equipment next week
- Waiting for release from ALS EH&S group
- Will install during the present shutdown
- Complete by December

## Scope, Boundaries and Responsibilities

- LBNL will deliver
- 4 chambers with electronics for IP1 and 5
- Gas control system
- DAQ with programming
- Installation support
- Hardware commissioning
- CERN will provide
- Local installation
- Gas supply and distribution
- HV and DC power supplies
- Control system integration
- VME64 infrastructure and DABIV boards

## Integration planning at CERN

- Complete system description
- Technical, installation, safety, electronics, responsibilities, deliverables...
- Met with all relevant parties at CERN
- Final draft at CERN
- EDMS process underway

## The case for IP2 and IP8

- LARP is providing four monitors which will be installed in IP1 and IP5
- LHC users have expressed written interest in having luminosity measurement capabilities at IP2 and IP8. These devices are viewed as machine items. LARP has already clearly stated to CERN it cannot provide for local installation and customization at IP2 and IP8
- LARP can provide more ionization chambers to CERN, which would be identical to those provided for IP1 and IP5 if CERN provides funds for the additional devices
- this would be cost effective if funded (by CERN) during the production of the 4 items funded by LARP, scheduled to begin in the summer of 2006
- LARP will not provide local installation in IP 2 and 8
- Installation and planning for using the devices at 2 and 8 is very different:
- these IPs don’t have TANs and will require a dedicated housing
- the supporting electronics is housed in areas not accessible during beam runs
- IP2 requires to have an unobstructed path of neutrons during the ion runs, adding complexity to the integration of the system
- CERN BDI group is working on finding an internal solution to the problem with no cost to LARP

## Current Plans for FY06

- Build one complete unit. This includes:
- Final design review (by April 06)
- a chamber, mating TAN bar, gas handling system, tunnel electronics package (pre-amps)
- Complete DAQ chain w. shapers, mezzanine boards and acquisition firmware integrated in CERN VME system
- no luminosity specific firmware/software
- Complete documentation of chamber production and electronic processing system
- Test existing prototype in RHIC
- Rad hard study and tests at FNAL (if possible)

## LUMI Milestones

**FY05**
- 	Complete high speed tests
- 	Complete conceptual design of FE electronics
- 	Complete and formalize system integration document
**FY06**
- 	Design and build first unit of DAQ system
- 	Final design of complete first unit
- 	Test prototype at RHIC
**FY07**
- 	Build all units
- 	Install and HW commission all units

## Lumi Budget Summary	

- Cost guidelines from task sheets (in $k):
- 	FY		04	  05	     06               07*
- Requested (LBL/BNL)	203	450   	1187/25         811/25->1063/25
- Received			395	 935
- *Note: FY07 budget to be finalized by April

## Tune Feedback

- Challenge: persistent current effects in SC magnets can strongly perturb machine lattice, especially during energy ramp (aka “snapback”). Effects for LHC predicted to be large.
- Betatron tunes (Qx,y) and chromaticities (Q’x,y=EdQx,y/dE) can vary significantly due to “snapback” resulting in beam loss, emittance growth.
- Solution:  make fast, precision Q, Q’ measurements and use these signals to feedback to tuning quadrupoles and sextupoles.
- This effort is ideally suited for a collaboration with RHIC, which can be the benchmark and testing ground for this effort.
- The Two Issues at RHIC:
- Dynamic Range
- Coupling

## Tune Feedback - Specification

- The goal is to control the tune during the acceleration ramp to avoid resonance crossing and beam loss
- The PLL method is to shake the beam and observe the resonant beam transfer function when the shaking frequency is at the fractional betatron tune
- Bunched beam Schottky signal studies
- Used to measure the stability of beam tunes during each cycle of the LHC

## Effects of persistent currents in RHIC

- Qx and Qx’ measured in RHIC

- Energy increasing

## The Approach - from RHIC to the LHC

- At RHIC
- resonant pickup, above the coherent spectrum
- defeated by transition - short bunches, fast orbit changes
- challenged by coupling - strong sextupoles, vertical orbit changes affect coupling, coupling drives tune feedback unstable
- AT LHC (and next generation RHIC)
- direct diode detection - mix all betatron lines to baseband, solves dynamic range problem
- measure all four eigenmode projections - results in PLL that is robust in the presence of coupling
- CERN and BNL personnel are actively collaborating on tune feedback and using RHIC as a platform for developing the system

## Overcoming Coupling

- Major issue (for both RHIC and LHC) is coupling, which drives the Tune Feedback loop unstable.
- Tune control (quadrupoles) is in horizontal and vertical planes
- Tune measurement is done with 'horizontal' and 'vertical' pickups
- Coupling can rotate the normal mode (or eigenmode) usually associated with horizontal plane into the vertical plane
- Typically, tune measurement consists of measuring just one of the two projections of a given eigenmode into horizontal and vertical
- However, planes of the normal modes of the tunes are determined by coupling
- At this point the Tune Feedback loop becomes unstable
- The measurement of amplitudes and phases of both projections gives sufficient information to correct for the effects of coupling, and have stable tune feedback

## Effects of Coupling

- C-A/AP/174 - Possible phase loop for the global betatron decoupling, Y. Luo et al
- C-A/AP/204 - Towards a Robust Phase Locked Loop Tune Feedback System, R. Jones et al
- both at http://www.rhichome.bnl.gov/AP/ap_notes/cad_ap_index.html

## Configuration - Tune and Coupling

- Tune
- PLL tune measurement operational at RHIC  for several years, automated, controlled by sequencer. Specialist checks status every few days.
- Used for ramp tune and chrom measurements, IR corrections, machine studies,...
- Coupling
- PLL re-configured to measure all
-     four eigenmode projections
- results in PLL that can be made
-     robust in the presence of coupling

## Results - 3D and PLL

- 3D (Direct Diode Detection) - installed at PS, SPS, Tevatron, RHIC
- solves dynamic range problem
- significant improvement in sensitivity
- greater sensitivity reveals 60Hz problem
- beam is excited horizontally at betatron line by line frequency harmonics
- excitation appears in vertical due to coupling
- It is at baseband, will show up everywhere in the spectrum - we can't escape it
- Required modulation of dipole current at harmonic ~300 is actually pretty small - one part in 1011
- Baseband PLL - loop closed, performance superior to present RHIC system, but locks on 60Hz lines

## Results from RHIC Run 5

- runs reliably under automatic sequencer control
- data quality appears sufficient for LHC needs
- Coupling correction
- measurement of all eigenmode projections in hand
- formalism and implementation ready for Run 6
- Mains harmonics
- shown that they arise from main dipoles
- recent CERN study indicates not a problem for LHC
- Baseband Tune Measurement (BBQ)
- Direct Diode Detection (3D) AFE solves dynamic range problem
- successful tune tracking up the ramp with VME-based BBQ, 'out of the box'

## Good results under sequencer control

******t**

******t**

**vert**

**horiz**

**+5**

**-5**

- dp/p of +/-10-4 gives ~+/-100 radial modulation (RHIC&LHC)

**-5**

**-5**

**+5**

**+5**

**Q'**

**Q'**

**Q'**

**ramp 6380**

**ramp 6382**

**ramp 6381**

- in RHIC modulation is at 1Hz

**Q1**

**Q2**

**Qy**

**Qx**

**r2**

**r1**

**d********2**

**d********1**

**Tune Feedback **
**would break here**

**PLL jumps eigenmodes here**

**Yun's and Rhodri's parameters **
**during tune crossing**

- Physical observables are the eigenmodes, which are what are measured by the tune measurement system. Eigenmode frequencies are determined by strength of both normal and skew quadrupole magnetic fields

- Previously, tune feedback adjusted strength of just normal quadrupoles (did not include skews) based upon incomplete measurement of eigentunes. Attempted to control Qx and Qy by measuring Q1 and Q2

- Measured eigentunes and 'set' tunes (calculated from complete measurement of eigentune projections)
- during a tune scan in RHIC

## TF - Integration Planning at CERN 

-  General statement
-         The US-LARP tune feedback task is to provide:
*the necessary instruments for the continuous measurement of tune, chromaticity and coupling in a robust way, with minimal emittance blow-up in the LHC.*
- These instruments shall be foreseen to allow for the rapid implementation of tune feedback in the LHC, and the possibility of subsequent chromaticity and coupling feedback.

- TF - Integration Planning at CERN

## Scope and Responsibilities

- CERN provides essentially all hardware
- kicker amplifiers, kickers, and pickups for LHC
- Direct Diode Detection AFEs
- Digitizer boards
- DAB64 Boards - FPGA for processing plus VME interface
- LHC (BPM, BLM, BCM,...) and LARP (PLL, Lumi, Schottky) standard
- VME crates and crate computers for CERN installation
- LARP provides all software up to LHC Control System
- VME crates and crate computers for LHC test installation at BNL
- gate array programming
- FEC programming
- LabVIEW control program, collaboration on LHC equivalent (FESA)
- specification and testing of LHC TF Applications software
- testing at RHIC, with and without beam
- pre-beam and beam commissioning support at LHC

## Milestones - Pt. Jeff Apr 05

- FY05
- 	Apr 05 - Preliminary Design Review - favorable
- 	Jun 05 - finalize prototype system architecture
- 		move from DAB (late Triumf delivery) to VME for prototype
- FY06
- 	Nov 05 - prototype (4 planes) ready for RHIC beam in VME
- 	Feb 06 - deliver 2 planes to CERN for SPS testing in DAB?
- 	Apr 06 - Final Design Review
- 	May 06 - SPS testing, initial Controls integration (FESA)
- 	Jun 06 - finalize architecture
- FY07
- 	Nov 06 - final system (4 planes) ready for RHIC beam
- 	Feb 07 - deliver final system to CERN, system integration and testing
- 	Summer 07 - system commissioning with beam

## Tune Feedback Budget Summary	

- Cost guidelines from task sheets (in $k):
- 	FY		04	05	    06             07*
- Requested (BNL/FNAL)	138	240/15   	300/35         325
- Received		100	122/15	 300/25
- *Note: FY07 budget to be finalized by April

## Issues - Funding

- Main problem is budget shortfall in FY06
- Caused in part by additional expenses due to a delay in the availability of the DAQ system from TRIUMF to CERN
- From the June DoE review:
- “*While the instrumentation items are a small part of the overall program, they are well-chosen and seem to be adequately supported at present. There was a sense, however, that the **instrumentation activities might be squeezed out by excessive demands from other parts of the LARP program** (magnets and/or commissioning). **LARP management must guard against this happening**, as these devices form an entry for the U.S. team into the arena of beam commissioning. “*
- A formal request ($261k/2yrs) has been made in October to address the problem

## Summary of Tune Feedback Status

- coupling problem solved by complete measurement of eigenmode projections
- dynamic range problem solved by direct diode detection (3D) analog front end
- ready with complete system (both rings) RHIC Run 6, intent is to implement tune feedback 'day one'
- Concern with late TRIUMF delivery of DAB board
- See below
- Concern with budget
- LARP management is addressing this
- Budget retune v.2c

## Common issue - Data Acquisition

- CERN requested that everyone uses the DAB-IV board as the interface point and responsible to provide these boards to the LARP instruments
- This impacts _all_ LARP instrumentation
- Such boards are under development at TRIUMF and the firmware that runs them is late
- LARP’s development can be negatively impacted by delays in DAB-IV boards
- LARP needs a minimum of 12-15 months with working DAB-IV boards to complete the necessary DAQ systems
- This has been communicated to CERN
- CERN recognizes the problem (impacts many CERN projects as well)
- LARP is working to set up video conferences and in person meetings to address the issue
- This caused cost increases in tune feedback
- Need a working solution by January to prevent a schedule delay

## Conclusions - Integration and Planning

- We have created the EDMS documents for both Lumi and Tune Feedback defining scope, responsibilities, interfaces and overall schedule
- Once entered, goes under configuration control at CERN
- Signoff of all stakeholders
- CERN involvement is increasing
- Actively participating to testing of both systems
- Plan to continue during the RHIC run
- US colliders continue to be a tremendous setting to develop and demonstrate these instruments
- RHIC in particular

## Conclusions - Challenges 

- Funding
- We are working with LARP management to continue securing adequate funding
- LARP management is committed to fix the Tune Feedback problem
- CERN is also well engaged
- Luminometry at IP2 and 8 is NOT scope creep
- LARP task sheets continue to define scope and budget year by year
- Funding requests are also managed through task sheets
- Detail ‘project’ reviews validate overall cost and schedule
- Integration with beam commissioning activities is essential to the survival of the instruments provided by the LARP collaboration and LARP is planning accordingly

## Summary

- LARP Instrumentation will build, commission, and integrate into LHC operations advanced instrumentation and diagnostics for helping LHC
- reach design energy
- reach design luminosity
- Strong collaborative efforts are in place and evolving
- Tune feedback is fully leveraging RHIC experience and includes CERN staff
- Lumi plans to do  the same with RHIC run 6
- Schottky’s experience at FNAL is a great asset
- synergies with BNL are fully leveraged
- This program will advance the US HEP program by
- Enhancing US accelerator skills
- Developing advanced diagnostic techniques that will apply to present and future US programs
- Help maximize LHC performance