bsrt optics design bi days 24 th november 2011 aurélie rabiller be-bi-pm

BSRTOptics Design

BI Days24th November 2011

Aurélie RabillerBE-BI-PM

BI Days 2011 - BSRT Optics Design 2

Summary

• BSRT Overview Light sources, optics

• Present system: spherical mirrors Advantages Limitations and encountered problems

• New system under study: lenses Advantages Limitations Abort gap monitor line modification


BSRT Layout

BSRT: Beam Synchrotron Radiation TelescopeBeam transverse profile monitoring with

synchrotron light

Optical line shared with: Abort gap monitor Longitudinal density monitor

Slow camera (BSRTS)

Fast camera (BSRTF)

Abort Gap Monitor (AGM)

Long. Density Monitor (LDM)

Optical delay line

Neutral filtersColor filters

Proton/Ion beam

90 %10 %

60 %40 %

10 %90 %

Motorized mirror

Extraction mirror

Two systems in LHC One system in lab


Synchrotron light sources

Light sources:• Dipole (edge to center): Visible light from 1.3 to 7 TeV• Undulator especially design to create visible light from 450 GeV to 1.3 TeV

Undulator Dipole D3Extraction mirror in beam pipe

Syncro light from und.

Syncro light from dipoleProton/ion beam

0m 0.7m 1.6m 6.3m 27.6m


Imaging system

• first focusing element: f= 4 - 5m inverted intermediate image with mag = 0.15 - 0.2

• second focusing element: f= 0.3 - 0.8m final image with mag = 0.3 - 0.6

28-32m 4-5m 0.5-1m 1-2m

ObjectIntermediate image

Final image

The system is limited by diffraction: the smaller the wavelength, the smaller the aberration => use of bandpass filters


Some pictures


Present design: spherical mirrors

1. Motorized 8 mirrors “trombone” to follow light source

2. Spherical mirror f=4000mm (F1)

3. Spherical mirror f=750mm (F2)

4. Cameras

• Total magnification: 0.3 (0.14 @ intermediate image plane)

F1

F2Entrance mirror

90%R Window

1

23

4


Present design: Advantages

No chromatic aberrations

PSF ≈ 18um for all wavelength’s

Object Plane

Image Plane

350nm: PSF = 18um 450nm: PSF = 18um


1mm

Image of 1mm grid object

S u r f a c e I M A : C a m e r a

100.00

O B J : 0 . 0 0 0 0 , 0 . 0 0 0 0 m m

I M A : 0 . 0 0 0 , 0 . 0 0 0 m m

0 . 3 5 0 0

A u r e l i e - B S R T - B 1 - 2 0 - 1 0 - 2 0 1 1 . z m xC o n f i g u r a t i o n 1 o f 1

S p o t D i a g r a m

2 3 / 1 1 / 2 0 1 1 U n i t s a r e µ m .F i e l d : 1R M S r a d i u s : 1 0 . 4 7 1G E O r a d i u s : 1 7 . 6 8 2S c a l e b a r : 1 0 0 R e f e r e n c e : C h i e f R a y


100.00

O B J : 0 . 0 0 0 0 , 0 . 0 0 0 0 m m

I M A : 0 . 0 0 0 , 0 . 0 0 0 m m

0 . 4 5 0 0





100.00

O B J : 0 . 0 0 0 0 , 0 . 0 0 0 0 m m

I M A : 0 . 0 0 0 , 0 . 0 0 0 m m

0 . 5 5 0 0





100.00

O B J : 0 . 0 0 0 0 , 0 . 0 0 0 0 m m

I M A : 0 . 0 0 0 , 0 . 0 0 0 m m

0 . 6 0 0 0




100

um

100

um

100

um

100

um


Present design: Limitations

• Aperture: only 26% efficiency @ 450GeV for one pass

trombone, even less with two pass trombone

• Alignment of the trombone really difficult and needs frequent

retuning => efficiency is even more reduced

• Transmission: 8 mirrors trombone = 30% intensity loss (even more @ 400nm)

Less light collected => larger bandpass filter=> bigger aberration due to diffraction



• Design in reflection

small angles in X plane, back and forth optical path’s really close to

each other

Tight space for inserting elements without intercepting the light

• Abort Gap coupled to BSRT

steering done with the 1st mirror, in common with BSRT



Emittance measurement:

At present, PSF is more than 300um and not constant

Possible causes:

Diffraction

Vibrations

Alignment changes

Idea: Simplify the optical system :

More reliable alignment

Reduce vibration


New design: Lenses

1. Lens optimized between 350 and 600nm, f=5000mm (L1)

2. 2 fold mirrors

3. Optimized lens f=300mm (L2) on motorized TS to follow light source

4. Camera

• Total magnification: 0.6 (0.21 @ intermediate image plane)

• Separate line for abort gap monitor by adding splitter before 1st mirror

1

2 3 4


New design: Advantages

• No more trombone: only 2 mirrors in the system instead of 8

=> intensity loss ≈ 10%

• Aperture increased: 1st lens closer to entrance mirror

=> efficiency @ 450 GeV ≈ 42%

• Much easier alignment

• No more small angles in X plane due to reflection: more room

for inserting elements

• Abort gap monitor decoupled: in view of future interlock

system


New design: Limitations

• Chromatic aberrations: lenses for 350 to 600nm region, but

not as good as spherical mirrors, PSF ≈30um

S u r f a c e I M A : I M G

100.00

O B J : 0 . 0 0 0 0 , 0 . 0 0 0 0 m m

I M A : 0 . 0 0 0 , 0 . 0 0 0 m m

0 . 3 5 0 0

B S R T _ M a g 0 6 _ 0 5 - 0 9 - 2 0 1 1 _ C o r r e c t e d _ D o u b l e t 2 _ a n d _ F 3 0 0 _ 2 . z m xC o n f i g u r a t i o n 1 o f 1




100.00

O B J : 0 . 0 0 0 0 , 0 . 0 0 0 0 m m

I M A : 0 . 0 0 0 , 0 . 0 0 0 m m

0 . 5 5 0 0



2 3 / 1 1 / 2 0 1 1 U n i t s a r e µ m .F i e l d : 1R M S r a d i u s : 7 . 7 0 0G E O r a d i u s : 2 4 . 4 8 4S c a l e b a r : 1 0 0 R e f e r e n c e : C h i e f R a y


550nm: PSF = 25um 600nm: PSF = 57um Image of 1mm grid object


100.00

O B J : 0 . 0 0 0 0 , 0 . 0 0 0 0 m m

I M A : 0 . 0 0 0 , 0 . 0 0 0 m m

0 . 4 5 0 0





100.00

O B J : 0 . 0 0 0 0 , 0 . 0 0 0 0 m m

I M A : 0 . 0 0 0 , 0 . 0 0 0 m m

0 . 6 0 0 0




1mm

100

um

100

um

100

um

100

um


New Design for Abort Gap

• Beam splitter T=92% above entrance mirror

• F=2000mm plano-convex lens

• 2 fold mirrors (one motorized)

• Camera to check beam presence and alignment


Lab and tunnel test plan

BSRT:

Test in lab to validate the system as completely as possible

Magnification, aberrations, transmission, alignment procedure...

Abort Gap Monitor:

Test in lab (mostly alignment procedure)

Installation in the tunnel on one side during the shutdown

In addition to the present system


BSRT in LHC

D3 Dipole

Sync. Rad. Monitors

SC Undulator

bsrt optics design bi days 24 th november 2011 aurélie rabiller be-bi-pm

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