MIRROR-1: yes to both details in the description

[decarlof]

MIRROR-1: yes to both — 2bma:m3 is held at one fixed position in Mono (m3 = 1.0 mm, stripe a Pt, all 6 Mono energies) and swept per energy in Pink (m3 = 3.039 / 13.0 / 39.0 / 49.0 at 30 / 40 / 50 / 60 keV, with coordinated table-X at 60 keV); stripe-to-position map below (inferred from Bragg λ = 2d sin θ cross-check; operator confirmation pending)

MIRROR-1: All three sub-questions answered yes, with a concrete stripe-to-position map.

(1) Mono mode — held at one fixed position

From the live energy2bm.json store_0 (decarlof/energy fork, per ENERGY-3 / cora#252), all 6 Mono-calibrated energies carry identical mirror-side positions:

Mono energy	m3 (m1_horizontal)	m1mox / m1m2x (table X)	m1angl	m1avg
13.374 → 25.584 keV (all 6)	1.0 mm	8.0 / 8.0 mm	2.615 mrad	0.0 mm

So the mirror is held in a fixed configuration in Mono — the IOC re-asserts the same five values on every Mono energy change, the DMM downstream is what does the per-energy monochromatic selection. The held stripe is a (Pt single-layer) per the stripe-to-position map below.

(2) Pink mode — swept per energy

Pink-mode values vary per energy for m3 and (at the highest energy) table X:

Pink energy	m3 (m1_horizontal)	m1mox / m1m2x (table X)	m1angl	m1avg
30.000	3.039 mm	8.0 / 8.0	2.615 mrad	0.0
40.000	13.0 mm	10.0 / 10.0	2.615 mrad	0.0
50.000	39.0 mm	10.0 / 10.0	2.615 mrad	0.0
60.000	49.0 mm	29.0 / 29.0 mm	2.615 mrad	0.0

Mirror angle (m1angl = 2.615 mrad) is constant across all 10 calibrated energies — Mono and Pink — so the per-energy variation in Pink mode is purely a lateral substrate translation (m3) plus a coordinated table-X extension at the highest energy.

Per ENERGY-5 / cora#254: the DMM lateral X motors (m25 / m28) are NOT involved in stripe selection (they're alignment positions); the mirror's m3 IS the stripe selector.

(3) Stripe-to-position map

Cross-checked the four m3 positions against the Bragg resonance condition λ = 2d sin θ at the operational pink-mode mirror angle (m1angl = 2.615 mrad):

Stripe	Coating	d-spacing	m3 [mm]	Table X [mm]	Pink calibrated energy	Bragg-calc resonance
a	5 nm Pt single-layer	n/a (single layer)	1.0 (Mono) / 3.039 (Pink 30)	8.0	All 6 Mono + Pink 30	Pt critical-angle cutoff ≈ 21 keV at 2.615 mrad; broadband below cutoff
b	W(1.2 nm) / Si(5.37 nm) × 50	6.57 nm	13.0	10.0	Pink 40	36.1 keV (slight detuning from 40 keV)
c	W(1.2 nm) / Si(3.56 nm) × 50	4.76 nm	39.0	10.0	Pink 50	49.8 keV (clean match)
d	W(1.2 nm) / Si(2.73 nm) × 50	3.93 nm	49.0 + table-X coord	29.0	Pink 60	60.3 keV (clean match)

The Bragg-resonance values matching the calibrated energies to within ~10% (and within 1% for stripes c and d) is strong evidence for the stripe assignments. Stripe a is used both for Mono (held) and Pink 30 keV (just slightly past the Pt critical-angle cutoff, presumably operating in the Pt-reflectivity rolloff band). The Pt → stripe b → c → d sequence walks up in energy as expe
cted for a multilayer mirror selector.

Operator confirmation worth getting:

• Visual confirmation that m3 = 1.0 mm puts stripe a in the beam, m3 = 13 mm puts stripe b, etc.
• Stripe widths and the inter-stripe spacing on the substrate (would explain the 10/26/10 mm jumps in m3).
• Whether the slight detuning at 40 keV (calc 36 keV vs calibrated 40 keV) is intentional (perhaps the operator picked a working-point on the multilayer reflectivity curve rather than the peak).

NOT freely operator-selectable

The cora question asks whether stripe selection is "a freely-selectable discrete pick" — operationally, no. The energy-change IOC re-asserts the calibrated m3 value on every energy change (see ENERGY-3 / cora#252); the table determines which stripe sits at which (mode, energy) tuple. Switching to a different stripe at a given energy me
ans either:

• Adding a new calibrated energy at the target stripe via energy add --energy <value> (per ENERGY-8 / cora#257 and the follow-up comment on cora#256).
• Manually driving m3 outside the energy-change flow (operationally rare; would also need a compatible mirror angle and possibly recalibration of the downstream DMM if in Mono).

CORA-side application

Cora's existing assumption ("energy/mode-dependent stripe; held in Mono, swept in Pink; no stripe → position map on file") is structurally correct; this ticket fills in the position map:

• Mode-dependent stripe selector axis: model m3 as the active stripe selector. In Mono, the value is constant (1.0 mm); in Pink, it's a 4-point per-energy curve. Same shape as the per-energy axes for m30 / m31 / m32 (DMM Bragg arms / M2 Y) — see ENERGY-1 / cora#249.
• Coordinated table-X: m1mox / m1m2x (mapped onto 2bma:m1 and 2bma:m4) need to be modelled together with m3 for the Pink 60 keV case — they jump from 10.0 to 29.0 mm coordinated with the m3 = 49.0 move.
• Stripe-to-position map as a static field on the M1 Asset: each stripe a / b / c / d with its d-spacing, the m3-range it occupies (~3.039 for a / ~13 for b / ~39 for c / ~49 for d, ± stripe half-width), and the calibrated energy it covers in Pink. This is the analogue of how cora modelled the DMM stripe geometry in ENERGY-6 / cora#255.
• Mirror angle (m1angl) constant at 2.615 mrad: not a per-energy variable for the mirror itself (the per-energy "angle" is encoded in the DMM Bragg arms downstream in Mono; in Pink there's no per-energy angle change at all — the stripe selection IS the per-energy degree of freedom).

Downstream alignment

The Mirror M1 in-vacuum stripe selector block in item_020.rst (latest commit pending) now carries:

• The 4-stripe definitions (already present).
• A new "Stripe-to-position map" sub-section with the table above (m3 + table-X values per stripe per mode, plus the Bragg-calc cross-check).
• Explicit Mono-vs-Pink behaviour annotations.
• A note that the selection is NOT freely operator-selectable at run time.

Cross-references

• ENERGY-3 / cora#252 — saved-table mechanism (the m3 values per Pink energy are stored in energy2bm.json store_0 and loaded on every energy change).
• ENERGY-5 / cora#254 — DMM m25 / m28 are NOT stripe selectors (cora's parenthetical was on the DMM side; the stripe selector is on the Mirror, this issue).
• ENERGY-6 / cora#255 — DMM substrate has its own two stripes (13.8 / 24 Å), independent question from the mirror stripes here.
• ENERGY-8 / cora#257 — calibration-via-energy-add mechanism (how to add a new (mode, energy, stripe) calibrated point if needed).
• [MODE-3 / cora#TBD] — the cora question parallel to this one but framed as a beam-mode rather than mirror-stripe question; same Pink-mode m3 + table-X data.

Net

MIRROR-1 answer: yes to both — stripe held in Mono (m3 = 1.0, stripe a Pt, across all 6 Mono energies) and swept per energy in Pink (m3 walks 3.039 → 13.0 → 39.0 → 49.0 at 30 / 40 / 50 / 60 keV, with coordinated table-X kicking in at 60 keV). Selection is calibration-table-driven (re-asserted at every energy change), not freely operator-selectable at run time.
Stripe-to-position map confirmed via Bragg resonance cross-check at θ = 2.615 mrad mirror angle.

[xmap]

Resolved by #295 (merged). The mirror coating-stripe selector is modeled as the Mirror_StripeReachX PseudoAxis facet (held at stripe a in Mono, swept per Pink energy 3.039/13/39/49) with the named-stripe-to-position map (a Pt; b/c/d W-Si + d-spacings) on the Mirror descriptor.