Planning the heavy-ion beam test at INFN

Solar ion fluence required in the beam test

• Scale factors between a test chip "top5" and the entire GLAST
  • 10 years = 3650 days of operation
  • Safety margin of factor of 10
  • "Area" factors

    	top5	entire GLAST *	scale factor
    Analog area (# signal lines)	3	884736	2.95 x 105
    Digital area (cm2)	2.80 x 10-3	8.65 x 102	3.09 x 105
    # bits in control registers	32	2914560	9.11 x 104

    *) Values of the entire GLAST are estimated from a layout of a test chip, GTFE64d.
  • Total factor = 3650 days x 10 x 3.09 x 10⁵ = 1.13 x 10 ¹⁰ days
• Expected particle flux in orbit and ion fluence required in the beam test

  LET (MeV cm2 mg-1)	Particle flux at the worst Solar events (ions cm-2 day-1)	Solar fluence* (ions cm-2)	ion species available in the beam test
  1.4	3 x 10-1	3 x 109	12C
  2.9	2 x 10-2	2 x 10 8	16O
  3.6	8 x 10-3	9 x 107	19F
  8.5	2 x 10-3	2 x 107	28Si
  12.4	1.5 x 10-3	1.7 x 107	35Cl
  26.5	8 x 10-4	9 x 106	58Ni
  53	2 x 10-4	2 x 106	107Ag
  80	5 x 10-5	6 x 105	197Au

  *) Solar fluence is particle flux at the worst Solar events multiplied by the largest total scale factor estimated above, or 1.13 x 10 ¹⁰ days.

Expected SEE frequency

• Summary of the SEE test results at NRL

  ion	surface LET (MeV cm2 mg-1)	SEE-vulnerable spot*		Expected SEE frequency per ion flux**
  		SEU	SEL	SEU (ions-1 cm2)	SEL (ions-1 cm2)
  12C	1.4	None	None	0	0
  16O	2.9	None (1B?)	None	0 (2.5 x 10-7 ?)	0
  19F	3.6	None (1B?)	None	0 (2.5 x 10-7 ?)	0
  28Si	8.5	1B, 1C, 2B	None	7.5 x 10-7	0
  35Cl	12.4	1B, 1C, 2B, 4B	None	1.00 x 10-6	0
  58Ni	26.5	1B, 1C, 2B, 4B	None	1.00 x 10-6	0
  107Ag	53	1B, 1C, 2B, 4B	None	1.00 x 10-6	0
  197Au	80	1B, 1C, 2B, 4B, 2C, 2D	None	1.51 x 10-6	0

  *) For spot ID's, see our web page on the results of the SEE tests at NRL.
  **) Expected SEE frequency is estimated based on the results of the SEE tests at NRL performed in June 2001.
• Choice of ion flux and SEE expectation in the beam test at INFN

  ion	surface LET (MeV cm2 mg-1)	ion flux (ions cm-2 s-1)	expected SEE frequency		minimum exposure needed (s)
  			SEU (min-1)	SEL (min-1)	for 10 solar fluence	for the first SEU to be observed	for 10 SEU's
  12C	1.4	2.0 x 104	0	0	150k	1400	---
  16O	2.9	2.0 x 104	0 (0.30?)	0	10k	1400	(2000?)
  19F	3.6	2.0 x 104	0 (0.30?)	0	4600	1400	(2000?)
  28Si	8.5	1.0 x 104	0.45	0	2000	920	1330
  35Cl	12.4	1.0 x 104	0.60	0	1500	700	1000
  58Ni	26.5	1.0 x 104	0.60	0	900	700	1000
  107Ag	53	1.0 x 104	0.60	0	200	700	1000
  197Au	80	5.0 x 103	0.45	0	120	920	1330

Current test plan

• Perform the SEL study first, then the SEU study if possible.
• The total radiation dose should not exceed 10 krad for one chip.
• ¹²C and ¹⁶O will not be used in the SEL study. They may be used in the SEL study depending on results from other ion species.
• Exposure time for the full SEL/SEU study and their radiation dose

  ion	surface LET (MeV cm2 mg-1)	ion flux (ions cm-2 s-1)	SEL study		SEU study
  			exposure (s)	rad. dose (krad)	exposure (s)	rad. dose (krad)
  12C	1.4	2.0 x 104	---	---	1400	0.63
  16O	2.9	2.0 x 104	---	---	1400	1.3
  19F	3.6	2.0 x 104	4600	5.3	1400	1.6
  28Si	8.5	1.0 x 104	2000	2.7	2800	3.8
  35Cl	12.4	1.0 x 104	1500	3.0	2800	5.6
  58Ni	26.5	1.0 x 104	900	3.8	2800	11.9
  107Ag	53	1.0 x 104	200	1.7	2800	23.7
  197Au	80	5.0 x 103	1600	10.2	5600	35.8

• Test procedure
  1. First, we look for the SEL threshold of the chip.
     1. Try ¹⁹⁷Au for 5600 s (35.8 krad). Replace the test chip with a fresh one. Then, try ⁵⁶Ni for 900 s (3.8 krad).
     • If neither of them causes an SEL, then the SEL study is over (case 1).
     • If ¹⁹⁷Au causes SEL's, and ⁵⁶Ni does not, try ¹⁰⁷Ag for 200 s (1.7 krad). Then the SEL study is over (case 2).
     • If ⁵⁶Ni causes SEL's, proceed to the next step.
     2. Try ³⁵Cl for 2800 s (5.6 krad). This is for both the SEL and SEU studies.
        • If it causes SEL's, go to the next step.
        • If not, the SEL study is over (case 3).
     3. Replace the chip with a fresh one.
     4. Try ¹⁹F for 4600 s (5.3 krad).
        • If it causes SEL's, then the SEL study is over (case 4).
        • If not, try ²⁸Si for 2800 s (3.8 krad). Then the SEL study is over (case 5). The total dose for the third chip is 9.3 krad.
  2. Second, we look for the SEU threshold of the chip. However, what we can do for the SEU study depends on the total radiation dose in the SEL study. Table below shows possible situations of total radiation dose at the begining of the SEU study.
     • To plan the SEU study, use the SEU study planning chart (PostScript (67 kB), PDF file (21 kB)). Ask Mutsumi for how to use it.
     • The objective is to find the laser calibration coefficient, which is defined to relate laser energy deposition in the laser-beam test at NRL to equivalent LET in the ion-beam test at INFN. It is (LET in MeV cmE2 mgE-1) / (laser energy deposit in pJ) / 3.
     • Possible situations of total radiation dose at the begining of the SEU study

       	total dose (krad)		irradiated ions
       	2nd chip	3rd chip
       Case 1	3.8	0.0	197Au 5600 s, 900Ni 900 s*
       Case 2	5.5	0.0	197Au 5600 s, 900Ni 900 s*, 107Ag 200 s*
       Case 3	9.4	0.0	197Au 5600 s, 900Ni 900 s*, 35Cl 2800 s
       Case 4	9.4	5.3	197Au 5600 s, 900Ni 900 s*, 35Cl 2800 s, 19F 4600 s
       Case 5	9.4	9.1	197Au 5600 s, 900Ni 900 s*, 35Cl 2800 s, 19F 4600 s, 28Si 2800 s

       *) Note that these are not long enough for the full SEU study. You can still claim positive detection of SEU's if one SEU or more is observed. However, you cannot claim that the LET value is below an SEU threshold even if no SEU is observed.
  3. You are done!