1. ECAL Data Links • Preliminary Results of GOH Irradiation • CMS Week • ECAL Electronics Meeting • 16 Mar 2004

2. GOH GOH GOH GOH Irradiation Test Setup Ten GOH were irradiated in 60 MeV proton beam at PSI, 27-29 Feb. • One BERT GOH to observe any data errors. • Nine “sandwich” GOH to observe evolution of eye diagram vs. dose and also have some statistics in case of GOL or laser failure. BERT GOH (data, clock, I2C) “Sandwich” GOH(clock, I2C only) beam data data GIII Tx GOH eval board PC running LabVIEW control program “Sender” card data, clock, I2C clock Mothertest card I2C controller data deser eval board Rx eval board GIII Rx scope beam area control room ~30 m

3. Some photos In the control room Serious cabling Closeup of the GOH stack Setup in the beam area

4. Beam conditions • The BERT GOH was exposed to an integrated dose of 8 * 1013 p/cm2 over 25 hours. (Beam intensity measured by PSI.) • “Sandwich” GOH were progressively shielded according to their position in the stack. • Beam was steady except for two incidents that crashed the beam monitor. • Beam was well centered and aligned on the GOH stack (see later photo).

5. Data-taking • For the BERT GOH, we measured bit error rate continuously. • For the sandwich GOH, we recorded eye diagrams and measured eye opening every ~1013 p/cm2, at three bias settings. (9 x 9 x 3 = 243 measurements, by hand!) • GOH 4, at 4 * 1013 p/cm2: Bias current = 17mA Bias current = 13mA Bias current = 9 mA

6. Expected results • For all GOH: No dead GOH • For BERT GOH: No errors • For sandwich GOH: Increase in laser threshold current with increasing dose, but minimal change in laser efficiency (slope) minimal change in eye amplitude (as long as bias currents above threshold)  minimal effect on optical power budget. ΔIthr

7. Actual results: all GOH and BERT GOH • For all GOH: No dead GOH  • For BERT GOH: • At most ~5 errors over the entire experiment, but these all occurred exactly when changing bias currents for sandwich GOH, and so should probably be discounted. • After ~20 hours there was a third beam incident after which the BERT could not be recovered. Probably non-rad-hard electronics on the mother test board were killed despite the lead shielding.

8. Actual results: sandwich GOH - 1 • For sandwich GOH: • Eye amplitude stays roughly constant with increasing dose, as expected: • Shielding of GOH higher in the stack is evident both in the plots above and in the photo taken after irradiation:

9. Actual results: sandwich GOH - 2 • Also for sandwich GOH: • Extracting threshold current and efficiency from the previous plots: G. Dewhirst G. Dewhirst • Threshold current rises smoothly with dose, as expected, for GOH 1 to 4. GOH 5 to 9 appear shielded. • Efficiency (slope) is flat, as expected.

10. Conclusions • All GOH survived irradiation, with doses up to 8 * 1013 p/cm2 . • The BER observed was either extremely small (equivalent to 5 errors over the lifetime irradiation of ECAL) or zero. • The GOH behaved as expected with respect to threshold current, efficiency and eye amplitude vs. dose. • We plan to repeat these tests when we have assembled GOH with the CRT4T transistor.