P. Lenisa 1

The ”mature” targetThe ”mature” target(2000-2005)(2000-2005)

P. Lenisa – Università di Ferrara and INFN

Hermes End of Data Taking - Hamburg, 01.07.07

P. Lenisa 2

Data taking:Data taking:longitudinal runlongitudinal run

P. Lenisa 3

Deuterium 2000Deuterium 2000The “wonder” targetThe “wonder” target

• No T dependence of and Pa

•No recombination

•No wall depolarization

(SEC negligible)

• 8 months of perfect running

•HERA (no beam dumps)

•HERMES (no vacuum breaks)

•TARGET (no hardware failures)IDEAL target → no drawbacks from use of storage

cell

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Measured in the polarimeter

Avera

ge v

alu

e in

th

e

cell

The enemies of a bad cell:The enemies of a bad cell:Sampling correctionsSampling corrections

P. Lenisa 5

Measured in the polarimeter

Avera

ge v

alu

e in

th

e

cell

The enemies of a bad cell:The enemies of a bad cell:Sampling correctionsSampling corrections

No recombination and no depolarization

“The polarization we measure is exactly what the beam sees”

P. Lenisa 6

The beauty secret: waterThe beauty secret: water

• Excellent initial performance

• Improved with aging thanks to D20 covering

P. Lenisa 7

2003 reanalysis of 1997 hydrogen 2003 reanalysis of 1997 hydrogen datadata

“Now we understand our target”“Now we understand our target”

• 4 different data periods

• Use of limit for sampling corrections

• Use of measured value for molecular polarization (=Pm/Pa)

P. Lenisa 8

Summary of target performance.Summary of target performance.Longitudinal running.Longitudinal running.

Target/year H||(1997) D||(2000)

Pt 0.851 ± 0.033 0.845 ± 0.028

r 0.055 0.003 (absent)

PSE 0.035 ≤0.001 (absent)

PWD 0.02 ≤0.01 (absent)

PBI - -

t(1014 nucl/cm2)

0.7 2.1

FOM (P2t) 0.5 1.5

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Data taking:Data taking:transverse runtransverse run

P. Lenisa 10

Fourier analysis of e-bunch:–Resonance condition:

n

fi

h

EE

Depolarization

Longitudinal holding field

Transverse running: Transverse running: beam induced depolarizationbeam induced depolarization

P. Lenisa 11

Transverse running: Transverse running: beam induced depolarizationbeam induced depolarization

Transverse holding field

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Field intensity: 297 mT– B along z: 0.05 mT– B along y: 0.18 mT– B along x: 0.7 mT

(requested: B 0.15 mT)

Transverse magnet Transverse magnet

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Cell correction coilsCell correction coils

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Hydrogen 2003/04Hydrogen 2003/04The “hidden” beautyThe “hidden” beauty

• No recombination

• Minimal depolarization for an H target

• Target reached the FOM limit

P. Lenisa 15

Period 10/2003-03/2004

04/2004-07/2004

01/2005-04/2005

04/200511/2005

cell1 1 (warm-up) 2 3

Pt 0.786 ± 0.036

0.721 ±0.059

0.62 ±0.09

0.73 ±0.06

r absent absent 0.24 0.035

PSE 0.055 0.055 0.055 0.055

PWD 0.055 0.12 0.17 0.12

PBI ≤0.01 ≤0.01 ≤0.01 ≤0.01

t(1014nucl/cm2)

1.1 1.1 1.1 1.1

FOM (P2t) 0.7 0.6 0.4 0.6

Summary of target performance Summary of target performance Transverse running.Transverse running.

P. Lenisa 16

The cherries on theThe cherries on the (target) cake… (target) cake…

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Measurement of polarization of Measurement of polarization of recombined moleculesrecombined molecules

• Recombination on cell walls

• Impact on target polarization

• No measurements existing on recombination on an insulating surface (like Drifilm)

• Delicate measurement of surface physics

P. Lenisa 18

Tcell set to 260 K

(recombination increased)

Measurement’s principleMeasurement’s principle

=Pm/Pa

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ResultsResults

HERMES = Pa/Pm= 0.68±0.09stat±0.06syst

Pm=Pa=0.34±0.22 -> atoms on Drifilm surface are polarized (r ~ 14s)

P. Lenisa 20

First measurement of the spin-exchange First measurement of the spin-exchange collision cross-section in the low collision cross-section in the low

temperature regiontemperature region

• Spin-exchange collision:

two body process in which two atoms exchange their spins (conserving total angular momentum)

• Control of the cell temperature allows for variations of atomic gas temperature

• HERMES target unique tool for precision measurement of atomic polarization

P. Lenisa 21

• Pz+ injected (|1>, |4>)

spin-exchange collision |4> → |2> (Pz)

• Pz- injected (|2>, |3>)

spin-exchange collisions |2> → |4> (Pz)

↓spin exchange collisions

cause nuclear depolarization of the sample (Pz)

A measurement of Pz gives access to SE

Measurement’s principle IMeasurement’s principle I

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• Two depolarization mechanisms active in the cell

•Wall depolarization (density independent)

•Spin-exchange (density dependent)

Measurement’s principle IIMeasurement’s principle II

Decoupling of the two effects by intensity variation of the atomic beam

Pz=Pse

Pz=Pse

)21(

)1(2 2

sed

sese PnL

xP

P. Lenisa 23

HERMES data

ResultsResults

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Numbers…Numbers…

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Years Target DIS (Milion) Polarization

1996-1997 H|| 3.5 0.851 ± 0.033

1998-2000 D|| 10.2 0.845 ± 0.028

2001-2005 H ~6 0.74 ± 0.06

DataData

Best existing world sample

Only existing world sample

P. Lenisa 26

Label No. Size Installed Last

3 1 29.8x9.8 04/96 12

4 2 “ 04/97 5

4 2 ” 12/97 4

5 3 “ 08/97 5

6 4 “ 04/98 11

8 5 19.8x8.0 01/99 1

7 6 29.8x9.8 02/99 9

11 7 “ 10/99 1

13 8 21.0x8.9 11/99 11

Fe1 9 “ 05/01 9

Fe2 10 “ 01/02 16

Fe5 11 “ 05/03 18

Fe6 12 “ 09/04 8

Fe4 13 “ 04/05 8

• 13 cells used • 9 months average last (1 min, 18 max)

• 20 produced• 50 man-months

CellsCells

The “innocent” victim

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RecordsRecords

2004

5 broken dissociator tubes

1999

4 beam dumps

(Total: 9 bad dumps)

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• 10 PhD thesis

• 7 diploma thesis

• 3 Collaboration papers

• 7 dedicated target papers

• (3 possible additional papers)

PapersPapers

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B. Braun, C. Baumgarten, I. Brunn, M. Capiluppi, V.Carassiti, G. Ciullo, G.

Court, P. Dalpiaz, D. Fick, A. Golendukhin, E. Garutti, G. Graw, W.

Haeberli, M. Henoch, R. Hertenberger, N. Koch, H. Kolster, H. Marukyan, R. Mussa, A. Nass, S. P. Pod’yachev, M.

Raithel, D. Reggiani, K. Rith, C. Simani, E. Steffens, J. Stenger, J.

Stewart, P. Tait, S. Tessarin, S.Wang, H. Ye, Y. Ye, T. Wise

22 senior physicists

10 PhD students

7 Diploma students

Manpower (1996-2005)Manpower (1996-2005)

(> 70 man years)

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Target awardsTarget awards

P. Lenisa 31

The best piece of artThe best piece of art

02.03.02 – TGA chamber opened after 8 years of operation

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The most original DESY aquariumThe most original DESY aquarium

07.02.03 – ABS flooded (50 liters of water)

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The most insane (realized) The most insane (realized) suggestionsuggestion

19.05.04 – 1680 minutes of uninterrupted TGA chopper wheel observation

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The biggest pig which entered East The biggest pig which entered East HallHall

15.08.05 – Spin and pork seminar

P. Lenisa 35

15.08.05 – Spin and pork seminar

The biggest pig which entered East The biggest pig which entered East HallHall

(dead)(dead)

P. Lenisa 36

The most courageous (crazy?) The most courageous (crazy?) intuitionintuition

“We will install an polarized internal target in HERA (with a storage cell) and measure its polarization with

3% absolute error”

Beginning 1988:

P. Lenisa 37

but up and running for but up and running for PAXPAX

(since 21.05.07)(since 21.05.07)

P.S.P.S.The HERMES target is not dead…The HERMES target is not dead…