S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing J.-F. Beche, J. Byrd, S. De Santis, P. Denes, M. Placidi,W. Turner, M. Zolotorev Lawrence Berkeley National Laboratory

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th All-in-One Tool for Synchrotron Rings Online measurement of bunch length and shape Bunch current – including nominally unfilled RF buckets (“ghost bunches”) Synchronous bunch position Fast: the results shown were accumulated in seconds/minutes Very wide dynamic range (10 4 )

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Summary Longitudinal Density Monitor overview –what it does, how it does it The hardware Experimental runs at the ALS Applications to LHC and NLC

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th A Brief History Original concept: femtoslicing experiments at the ALS (R. Schoenlein and M.Zolotorev, 2000) Prototype: LHC Accelerator Research Program ( ) Longitudinal dynamics studies in damping rings (?)

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th An Optical Sampling Scope Bunch Synchrotron Photons  1 Laser Photons  2 Mixed Photons  1 +  2 PMT Non-linear crystal [BBO] Filter(  1 +  2 ) laser pulse length << bunch length  1 +  2 = visible wavelength

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Scanning the Bunch Piezo-ceramic positioner  LHC: 40 MHz ALS: 71 MHz Laser L C/2L = 40 (or 71) MHz Adjust  by changing path length (phase modulation) mW diode-pumped laser ALS: 10 Hz ALS: 50 fs, LHC: 50 ps (10 W) LHC: 22 bins (std. mode) ALS: 32 bins

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Schematic (timing) Laser Synchrotron Light PMT PD ADC DAC Board Timing Cavity Control Processing +Interface (USB to PC) BBO Laser Timing Filter Ring main RF (PLL) Orbit clock

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th LDM – Electronics Board Layout Architecture – Different Boards –#1 : Phase modulation Generator –#2 : Phase Information Digitization –#3 : PMT pulse digitization –#4 : Delay generators/timing –#5 : Digital Backend (Storage and USB) 1234 To Laser Phase Offset From PMT From Photodiode PC 5

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Electronics - I. Mother Board with 71MHz clock board USB Control and histogram/average is fully operational

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Electronics - II. DAC Analog board for laser phase offset modulation Track and Hold board with self trigger for PMT pulse detection (only one bit is used in single photon counting mode) Actual Laser phase offset digitization board

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th DAQ PCI6534 National Instruments Standard DAQ Board Function Library Labview, C/C++ compatible Quad 8-bit I/O board, DMA transfer rates up to 20MHz (8, 16 or 32-bit)

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Tests at the ALS Bucket spacing 2 ns Bunch width ~50 ps “Camshaft” pulse 328 RF buckets filled Gap (LHC parameters) (2808/35640) ( ps) (2.5 ns)

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th wiggler bend magnet mirror synchrotron radiation e-beam Laser System BBO   2 = ~2 eV   1 = 1.55 eV   1 +   2 delay slit Optical layout at the ALS L = 800 nm, S = 638 nm  =355 nm Conversion efficiency is proportional to the laser power density and is optimized for = S

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th First Experimental Data (Nov. 2002) First data (Peak Height distribution) Electronics Setup

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th ALS Bunch Profile in Time SET3

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Zoom in... SET3

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Compress Scale... SET3

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Large dynamic range SET3

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Details

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Background Camshaft/Background ~ 10 3

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Synchronous Phase Transients SET3

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Bunch Length SET3

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th A Longitudinal Monitor for LHC 450 GeV - 7 TeV Untrapped beam fraction Protons in the abort gap Longitudinal bunch tails “Ghost bunch” population Etc.

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th LHC Applications of LDM Bunch core measurement (std. mode) Tails and “ghost bunches” (HS mode) 10 W 1064 nm Laser pulse period: 25 ns Laser pulse length: 50 ps LHC length: 88.9 µs Photons/bunch/turn: 10’s ( nm) at full current

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Bunch core measurement Measure bunch population at ±2  with 1% accuracy in a time short compared to the synchrotron period (~42 7 TeV) 22 bins required (50 ps x 22 ≈ ±2  ). Time required to map the core once: 22 turns ≈ 2 ms Expected population: 2· ·10 6 p/ps. Accuracy: %

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Tails and “ghost bunches” measurement Measure bunch populations as small as 2·10 4 p/ps all around the ring (causing background in experiments) with ~50% accuracy. Entire ring is mapped in 50 ps slices. Minimum number of turns: 500 (3556 slices/turn). At 7 TeV, (2±0.8)·10 4 p/ps give 3.2 ±1.8 counts in a 50 ps slice turns (< 100 ms) are required for the 50% accuracy as per specs. LDM is the ideal instrument...

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th NLC Damping Rings Parameters E = 1.9 GeV C = 300 m  z = 12 ps ∆t b = 1.4 ns N b = 576/714 (3 trains, 71 MHz can sample 20 bunches x train) S = (~300 turns) Long. damping time = 2.6 ms (2600/3 turns) Longitudinal dynamics in the machine never reaches a steady state + short bunches the LDM can be a valuable tool for understanding/monitoring the damping rings.

S. De Santis “Measurement of the Beam Longitudinal Profile in a Storage Ring by Non-Linear Laser Mixing” - BIW 2004 May, 5th Conclusions: Pros and Cons of LDM Fast sampling rate (laser cavity frequency) High dynamic range High time resolution (laser pulse length) Not limited to optical wavelengths Requires multi-turn sampling Requires synchrotron light Especially suited for dynamics studies in damping rings