# Presentation: 575461

## Top-Off: Advantages to user programs

- Tony Warwick  *ALS Experimental Systems Group*

-   Twofold increased average electron current
- 	increased brightness
-   Continuous operation
-   Constant thermal loading from bends and superbends
*    **electron beam life-time is no longer critical, leading to:*
-   Reduced vertical electron beam emittance
- 	increased brightness
-   Shorter bunches
- 	better TOF, better slicing
-   Small gap undulators (*electron beam life-time is no longer critical!)*
- 	increased spectral range
- 	increased brightness

## Top-Off: User Requirements

*User programs require:*
-   No detrimental thermal problems
-   Top-off also for camshaft and single bunch
-   Minimal top-off injection transients
-   Top-off injection in a single booster cycle
-   30 seconds between top-off injections
-   Gating for experiments sensitive to top-off transients

- Requirements were discussed during tests conducted December 2003, January 2004 and April 2004

## Top-off injection with reduced vertical emittance

- i  	t   	t   	v  	h	v	`h	`v
- 1.5mA	72.0s	≤50ms	150x10-12	298m	23m	22rad	6rad
- 1.5mA	32.0s	≤50ms	30x10-12	298m	8m*****	22rad***** 	3rad*****
- 1.5mA	14.4s	≤50ms	5x10-12	298m	4m	22rad	1rad

- _coupling_
- Operational  03
- Intermediate
- Smallest Ever

****diffraction limited below 310eV***

## Sagittal first mirror essential for soft x-rays

-   Preserves vertical brightness       ***v**=8****m: diffraction limited below 310eV*
-   Horizontal deflection facilitates chicane straights

-   Cylindrical first mirror should deflect horizontally (vertical focussing)

## 50mm period, 37 periods, K=5.3, 500mA, 1.9GeV

**Mirror 10m from source, 1.5 degrees grazing**

- 200mm

- 3.8mm FWHM

**horizontal deflection**

**Undulator beamlines: first mirror thermal load**

## Sagittal first mirror for undulators

**Sagittal first mirror for undulators**

*Internally cooled glidcop with pressure-free water feed (ALS engineering)*

## Double Front-End for chicaned undulators

- (add fabrication
- and fiducialization
- tolerances)

- clip and view on phosphor without front end shadow

-  K/ =  471rad
- K=1.75, =3718 (1.9GeV)

- ( 273rad)

-  273rad

- mirror mask apertures are 6x of largest operational undulator central cone

**front end masks**

**mirror mask**

**mirror**

**Double Front-End for chicaned undulators**

**mirror**

## Chicaned undulator beam lines

**Chicaned undulator beam lines**

- Sector 11.0
*two 50mm EPUs*
*first is operational 11.0.2 (MES)*
*second operates spring 2005 11.0.1 (PEEM3)*
*experiment equipment coexists on the floor*

## Superbend beamlines: constant thermal load

- Bent mirrors will experience constant thermal load

## Undulators with smaller gaps

**Undulators with smaller gaps**

- 50mm period EPU outside vacuum (11.0.1)
*With top-off, can reduce magnetic gap from 14.5 to 10mm, (5mm vertical aperture)*

- In-vacuum undulator from Sumitomo, 1.4Tesla 5.5mm gap

- Superconducting undulator ‘in vacuum’ 6.5mm magnetic gap LBNL LDRD program

## Undulators with smaller gaps: EPU

- Intermediate coupling  σv=8μm

## Undulators with smaller gaps: SC undulator

- Intermediate coupling  σv=8μm

## Injection Tests for Top Off	    ...summary

- Three test conditions were run, with various beam lines looking at the effects:
**	****Condition 1 normal operation.**
**	****Condition 2 injection bumps and septa pulsing.**
**	****Condition 3 injection bumps only.**
- The septum magnets are known to leak field and affect the position of the stored beam, if this problem is solved then condition 3 will best represent top-off operation.
- No beam was actually injected during these tests. Observed variations in experiment count rates are due to transient distortions of the closed orbit.

## Effects of bump magnets on closed orbit

## Effects of septa on closed orbit

## Top off tests: BL 4.0 ( 1 Hz   1/26/04 )

- Intensity of the x-rays was determined by measuring the photo-current from a gold mesh
- Each data point was integrated for 1 second using a picoammeter and a V/F converter
- Each region (condition) was scaled to unity and offset for clarity

***‘******condition 2’ = septum on, we can see intensity fluctuations, expect these to be gone when septum field leakage is reduced***

*Tony Young and Elke Arenholz*

**Top off tests: BL 4.0 ( 1 Hz   1/26/04 )**

## Top off tests: BL 7.3.3 ( 1 Hz   1/26/04 )

- Typical Co NEXAFS spectra measured with PEEM-2 on 30x30 m2 area
- Exposure time per point: 2s

***we cannot see any effect here***

*Andreas Scholl*

**Top off tests: BL 7.3.3 ( 1 Hz   1/26/04 )**

## BL11.0.2

**100 ms**

**BL11.0.2**

**Top off tests: BL 11.0.2  ( 1Hz   12/7/2003 )**

- Gating seems to be a requirement for these sensitive experiments. For example, in STXM the microscope scans a horizontal line of the image and the vertical image position is stepped one pixel while the horizontal scanner resets for the next horizontal line. The inhibit gate will inform the microscope computer that an injection has occurred and the next vertical step will be inhibited. The next horizontal line scan will be a repeat and the corrupted line will be overwritten.

- Second “Injection” test STXM 11.0.2Septum magnet turned off
***injection transients will cause an intensity fluctuation during a horizontal line scan in STXM at beam line 11.0.2***
- One horizontal line scan takes 60 ms

## Top-Off: Advantages to user programs

- Tony Warwick  *ALS Experimental Systems Group*

-   Twofold increased average electron current
- 	increased brightness
-   Continuous operation
-   Constant thermal loading from bends and superbends
*    **electron beam life-time is no longer critical, leading to:*
-   Reduced vertical electron beam emittance
- 	increased brightness
-   Shorter bunches
- 	better TOF, better slicing
-   Small gap undulators (*electron beam life-time is no longer critical!)*
- 	increased spectral range
- 	increased brightness

## Top off tests: BL 6.3.2

- Signal measured after vertical slit offset in X by 160 microns from  the center of the beam in the endstation. One point every 0.6 sec.

- Erik Gullikson

## Undulators with smaller gaps

## Original soft-xray undulator beam lines cannot preserve reduced vertical source size

- First mirror, deflects vertically, focus on entrance slit
- Goals: high spectral resolution---narrow slit---maximum transmission---minimum demagnification---minimum aberration

- D ≈ 15m   θ ≈ 2°   Δthermal 1994 1.5GeV ≈ 2μrad
- 2 D Δ ≈ 30 μm

- Reduced vertical source size requires improvements at 7.0, 8.0, 9.0, 9.3.2, 10.0

- undulator source