TL;DR: Enough strength for Molecular prime 75% slow (Max), Enough Duration for Null Star 90% damage reduction (Max).
You NEED 1 Archon Crimson shard 10% Duration and a Rank 5 Molt Efficiency (36% Duration) to achieve 300% Duration.
Recommended 4 Archon Azure shard , x2 50 Mana and x2 Mana/Armor/Health

Fast Nova Build:
https://overframe.gg/build/379965/

There are two goals to achieve as a slow [Nova Prime]: Duration 300% and Strength 145%. Be ready, as I'll guide you in how to achieve the max benefit of your antimatter lady and become the Crème de la crème [Nova Prime] you always wanted to be.
The slow [Nova Prime] build consist, as the name indicates, to slow enemies with Molecular prime. But why Duration and Strength are important for the Slow Build?

Molecular prime releases a Slowing (Slow Nova) wave that starts at 5 m from Nova and it propagates to the enemies at a 5 m / s rate during 6 s (base max rank). Range does not increase the expansion of the wave, BUT duration does.
Higher durations = Longer distance the wave covers.
The amount of strength Nova has at the moment of Molecular prime activation decides the enemy movement speed/attack speed modifier. With a base strength of 100%, the enemies are 30% slowed. The maximum slow debuff cannot exceed 75%, which is reached with 145% strength.
On the other hand, if strength goes below 70%, enemies will be faster instead (Fast [Nova Prime]).
In order to achieve the 145% strength, I highly recommend using the 3 umbra mods: [Umbral Fiber], [Umbral Vitality] and [Umbral Intensify]. [Umbral Intensify] grants you 44% strength at rank 10 when used alone, and 77% when used with fiber and vitality. We only require 45% strength and this could be achieved by using a combination of Crimson Shards and/or [Power Drift], however the extra +220% Health and +55% armor provided by using the 3 umbra mods are far superior than changing [Umbral Intensify] for a different survival mod. If a better survival mod is released, replacement of [Umbral Intensify] should be consider, but at the time of this build being written, this is the best option.
In addition, for this build we are subsuming Eclipse into Wormhole, so the extra strength help us to get more Damage Bonus/Reduction.

Null star creates 6 (Base max rank) antimatter particles that orbit around yourself and only attack if enemies are located at 12 m (Base max rank) away, every second. When the particles are orbiting the warframe, each one of them grant 5% Damage reduction to the health, with a Max damage reduction of 90% with 20 particles.
The amount of particles created is affected by Duration and in order to create the 20 particles, a Duration of 300% is required.
For this build, we are using 254% duration through mods, 36% with Molt Efficiency and 10% with a single Crimson Archon Shard 10% Duration for a total 300% Duration.

For the subsumed abilities, I recommend Eclipse > Roar > Dispensary. You can subsume Antimatter Drop instead of Wormhole.
For Exilus slot, [Endurance Drift] is a nice QOL mod to have. Options would be Escape Velocity (If you didnt remove Wormhole) or Power drift to boost Eclipse/Roar a bit more.

Aura Mod is more of a preference choice and the Aura Forma used here is to make this build compatible with Fast Nova Prime build. I prefer Corrosive projection for the -18% Armor reduction, but [Physique], [Steel Charge], [Swift Momentum] or [Growing Power] are good options too.

[Molecular Fission] is required to have Null Star active almost 100% of the time.
[Adaptation] is a very useful mod to reduce damage.
[Rolling Guard] provides a nice 3s invulnerability window and status removal.
Arcane Energize so you never run out of mana, can be changed for a more offensive arcane according to preferences.